First things first: I'm going to skip the "spells" chapter, as it's mostly standard spells.
There is a metric ton of good in this book. For a 64-page volume, it's packed to the gills with stuff. The obvious is level advancement to 30 and beyond. This is a given for a Companion set, and the B/X Companion delivers. Most of the advancements are bog-standard (spells to 9th level, etc.) but what impressed me was the thief advancement, which includes all those mysteriously-promised-but-never-delivered new abilities like ventriloquism, disguise, and other such "infiltration" style abilities. Great stuff.
Following this, we have a section on adventuring at high levels. Much of the advice herein is standard, but the presentation is stellar. Interestingly, it takes a stance that few versions of old-school D&D-styled games have when it says that XP should never be given for gold. Such a ruling greatly slows down character advancement, but is a rule which I appreciate. It also discusses how XP is only granted for actual adventuring and personal conquest, never for the day-to-day running of a domain, even if such running means sending your army to war. You don't get experience because your army wins battles--only if you actually fight in the battle and acquire personal victories therein, such as defeating an enemy general in single combat, or slaying the other side's pet dragon. I like this take, as it well represents the idea of the slothful ruler who was once great but now has fallen into laziness and ineffectiveness.
Along these same lines are the idea of "upkeep costs." Long a common idea in the RPGA's Living Campaigns, and even games such as Mongoose's take on the Conan mythos, it now becomes a part of the Moldvay/Cook/Marsh canon (if you consider B/X Companion a part of that canon, and in my opinion there's absolutely no reason not to). The cost is 1% of the character's total XP per year of adventuring (presumably figured at the end of that year). This should serve to keep adventurers working within modest means as they struggle to build the funds to eventually achieve domain rulership. The total is solid; I have a small issue with the execution which I'll get to in the next section, below.
Another good inclusion here is a list of new specialists, hirelings, and retainers including assassins and court magi.
Next we get into what could be called the real meat of the book: high level encounters. This section is arguably dominated by rules for mass combat, which are pretty spectacular, actually. Very intuitive and easy to handle, unlike many unit-based combat systems out there today. This system does not even require miniatures to use (though I would argue that at very least a map of the battle area and forces is a requisite), but it could, if desired, be very easily turned into a pretty damn fine miniatures battle game, and a few suggestions for those desiring the use of minis are included in the text. Essentially the rules break down armies into units of similarly armed and trained troops (so cavalry, infantry, archers, elves, dwarves, etc.) with each having its own benefits and drawbacks based on the overall abilities of members of the unit (Calvary units, for example, have low AC, high "to hit" probabilities and the ability to charge but are vulnerable to set spears). Instead of making attack rolls, the rules assign a "to hit" percentage to each unit. This percentage modifies the unit's damage roll, reflecting how many members of the unit actually manage to inflict casualties to the other side. Damage is rolled, the % modifier applied, and the result subtracted from the opposing unit's hit points, which are simply the average hit dice totals of each member of the unit, added together. For example, a unit of human infantry would be fighters with a d8 hit points. If there are 50 members in the unit, the unit would have 50 x 4 = 200 hit points. If a cavalry unit of 3rd level warriors attacked the fighters (say, AC 5) with lances dealing 1d8 damage, and the unit had 20 mounted warriors, the resultant roll would be 1d8 x 20, modified by the percentage modifier for the cavalry cross-referenced on a matrix with the armor worn by the opposing unit. In this case, consulting the matrix I see that a 3rd level unit vs. AC 5 defenders = 45%. So if the damage roll was 5, the roll would do (5 x 20) x .45, or 45 points of damage.
If there is a weak point to this system, it's that it'd be something of a pain to continually track how many warriors were left in a given unit based on how many hit points the unit had lost--this would require recalculating after every hit, but I have the sense that after a few battles this would become second nature.
Rules are also included for breaking the mass combat down for player characters to perform individual acts of heroism (which they are expected to do, lest they impose a penalty to their army's morale!), sieges, and many other eventualities on the battlefield. In a book chock full of great stuff, these mass combat rules are the standout highlight.
After the section on characters and adventuring, we get to new monsters. The focus, of course, are on what in modern parlance would be termed "Epic level" play, so the monsters tend to be high-powered. There are some very clever takes on classic monsters here, some with the serial numbers filed off to give you a new twist on a classic monster. An example is the Lich, which while it remains an undead wizard, loses its phylactery (a D&D-ism) and takes on a more pulp literature bent, reminiscent of the presentations of undead wizards in the works of Robert E. Howard, H.P. Lovecraft, and Ambrose Bierce. The Vampire Lord, of course, is a must-have for a high-level campaign, though there's little surprising about this monster. Other notables include Black Orcs, which are orcs of a more Tolkien variety, the Bane Lord, which will sound familiar as a gigantic demon wreathed in flame who carries a flaming sword and scourge, the Death Lord, familiar as a fallen-Paladin-turned-undead, and some favorites that have never appeared in a D&D core product before (only in adventure modules): the Bandersnatch, Ju-Ju Bird, and Jabberwock! The monster section alone makes this worth the price of entry.
After the monsters is a fairly extensive section with new magic items. There are a lot of standards here, as well as some nifty new stuff. But my favorite inclusions were, as with the monsters, serial-numbers-off versions of immediately recognizable, iconic weapons. For example, the "Wyrm Lance," a legendary lance forged by magic that are designed specifically to combat dragons. The Companion also has extensive writeups of magical tomes, manuals and grimoires which is a welcome addition, albeit one that you probably never really noticed was lacking before.
Finally, there are sections on Dungeon Master Information and Special Adventures. There's not a lot to report in these sections--the advice, while obligatory, is largely the kind of advice that in the modern era DMs have figured out for themselves (establishing a cosmology, handling high-level adventures, ways to make environment an enemy, etc.) but one has to appreciate their inclusion as they make the game feel far more complete, and they pay homage to what the game is supposed to be: a continuation of the 1981 B/X rules. In addition, they are exceptionally well-presented and accessible for what they are, making them a valuable reference in their own right.
Now we move on to the things I did not like about the Companion rules. These are far fewer than the things I liked (always a good sign).
The first of these problems is the way Demihuman races are handled. I'll be honest: I abhor this treatment. It feels culled from the Mentzer take, and it just doesn't work for me. The idea that demihumans stop leveling (but they really don't, because they keep getting XP and improving their abilities) is just plain wonky. It would've been better, if the author chose to keep them powered down, to continue their advancement, albeit more slowly, and just stopped elves from gaining new spells. Even still, I think there's no reason demihumans couldn't have continued to advance normally--their advancement is already slower than humans and that unto itself is an effective restraint. So, instead of saying, "Elves stop advancing at level ten, but with every 250,000 additional XP an elf gets a +1 to attack with bows, and gets additional attacks when he accumulates..." just continue the level progression and indicate these advancements in the table. There's also no reason that elves, as creatures of magic, shouldn't get high level spells...they just get them much later as they advance more slowly. In the entire book, this is my single biggest gripe. I'm sure this was not the intent of the author, but it comes off feeling tacked on and lazy.
Upkeep Costs are the next in my "bad" section, and really this is just a nitpick. As I stated above, I love the idea, and the numbers work fine. What bugs me is the yearly implementation. Upkeep costs work better tracked by month. But again, a nitpick and easily fixed without changing anything else about the rules.
My next gripe is with the magic items and the way Manuals are handled. While other types of magic books are essentially usable once and then they go away, Manuals hang around. This means if you find a tome that increases your strength, everyone in the party is bound to increase their strength score. I am unable to recall if this was the case in older versions of the game, but to me it seems overpowered. I'd fix it by treating manuals as other magical books--once you read them, the text fades or the book vanishes.
The final gripe is that of the price point for the overall text. I understand fully the economics of small publishing, and why the cost is the way it is, but it has to be mentioned: even for a book this great, the high cost of $28 for a 64-page book is bound to be a turnoff to some people.
Remember, "The Ugly" in my reviews doesn't mean literally "ugly." It's just a blanket term for my review of the book's physical appearance. Let's start with the cover: this is a neat take. It naturally doesn't carry on the progression of the earlier two books (it can't, due to copyright reasons), but it pays a nice homage with new renderings of the three iconics that appear on these past books. If I had any nitpicky gripes about the cover art, they are twofold. The first is that I always thought the woman in red was an elf in the past, not a human. The second is that the cover art takes up the full bleed instead of being inside a window on a solid colored cover to match the presentation of the other two books...but the art overall is a gorgeous piece, and hot damn does it look fine sitting next to the B/X books.
This brings us to a general look at the interior art. This is all high quality stuff, and quite sufficiently "old school" in implementation and style so as not to pull one out of the mood you get when reading. Excellent art choices. Sparse illustrations but then, the original B/X books featured sparse illustration as well, so no complaints on that front.
Finally, we come to Layout. The layout in the book is, as one would expect, pretty basic, 2-columns with art, no background, exactly as it should be. I have only two nitpicks regarding layout (and these really are just nitpicks). The first is the font--the author uses standard Times New Roman font, when he should have, to keep presentation uniform with the other two books, used the Korinna font family. The second nitpick is that some of the sections begin on even instead of odd pages. Why is this an issue? Well, the old books were designed so that you could pull out the sections and organize them all into a binder, so that you would have Part 1: Introduction from the Basic and Expert rules together, then Part 2: PC Information from the B/X rules together, etc. Having the sections begin on even-numbered pages makes this impossible to do without photocopies and blank pages, even should you choose to 3-hole-punch your booklet. Again, however all of my gripes in this section are nitpicks.
Finally, when this project was originally announced, it was announced as a boxed set to go alongside the other two boxes. This puppy really, desperately needs a boxed set, with the book, a new adventure module (perhaps one that includes mass combat--call it "BXC1"), and maybe--just maybe--some old school dice from GameScience! Sure, this would push it probably to the $50 or more price point, but I would pay it in a heartbeat, particularly if the presentation matched those of the two earlier boxes.
Now, I have one content-related concern about this. The book does not make use of the OGL for production. It seems above board, but I have worries about the author getting slapped with cease & desist orders should WotC decide to get zealous about defending their copyrights and trademarks. This may well be undue paranoia on my part, but were I the author of this fine supplement, I would sincerely consider making use of the OGL in future releases, if for no other reason than to cover my behind.
The Final Score:
The final score: I give this book 4 1/2 out of 5. The only thing that keeps it from being 5 out of 5 is the handling of demihuman classes. Despite its high price point, this book is in every way the Companion set we were all promised way back in 1981 and have waited for, for all these years since. An outstanding piece of work in every way. I propose that B/X now be referred to as B/X/C, and that Moldvay/Cook/Marsh now be referred to as Moldvay/Cook/Marsh/Becker.