The pdf preview available here shows off 11 of the pages (almost a third of the product), so you know what you're getting... which is a thoroughly useful set of d30 tables covering quick character generation, dungeon features, monsters, and treasure. You might be able to generate an entire dungeon, in plenty of detail, with just this one book.
Replete with a useful table of contents, index, and hyperlinked bookmarks, this product can easily be used within 0e, B/X, and 1e systems. It includes a dungeon mapping key (with 98 symbols for architectural features, natural features, and furnishings), character attribute / motivation / inventory generators, dungeon walls / floors / doors / embellishment / debris generators, trap generator, poison generator, monster encounter tables and one-line monster descriptions for ‘at a glance’ lookup during games. (The latter are like the Monster & Treasure Assortment tables from TSR, but codified for d30 rolls.) Rounding out the collection are three pages of quick treasure horde generation tables (which facilitate easy conversion between 1e and B/X treasure types) and about eight pages of individual treasure item generators (including gems, jewelry, armor, weapons, and magic items). Even this short summary leaves out plenty of tables; you’ll have to discover them yourself (e.g., 1.45 billion potions; 27,000 mushrooms; 900 traps in 6 categories; 810,000 unique magical weapons, armor, and protective items, and so on).
At this point, you’re probably wondering, “So what’s the gimmick? Aren’t there lots of random tables already out there on the interwebs, produced for free by the denizens of the OSR?” Yes, there are, but LeBlanc has optimized these tables to get you maximally diverse output for minimal rolling. Promoting DM efficiency is one of the key goals that unifies the entire product. Most tables here utilize one of three conventions: (i) getting a single result from a single number (one d30 roll gets you one among thirty results; duh!), (ii) getting multiple results from a single number (e.g., one d30 roll gets you a particular trap type and a particular chance to detect it; that is, multiple results from the same table), and (iii) getting results from simultaneous 1d3 and 1d10 (e.g., one d30 roll gets you a poison with two independent features).
Here I must say that this method rocks when it comes to treasure horde generation. For instance, to roll treasure type A in the 1e MM, you typically had to do 8 rolls of percentile dice (1 for each category), and then – potentially – roll an additional 3d6, 8d10, and a d4 to get the specific treasure amounts. That’s twenty separate rolls! But using the treasure tables in the d30 Companion, you just roll eight times maximum to get the same result; the probability space is almost identical to that in the 1e MM (or B/X) in every respect. Multiply this across encounters and then across dungeon levels, and the time saved is pretty significant. LeBlanc lays out many of his other tables according to the same time-saving principles. In effect, he’s exploiting a traditionally underused die to save us lots of time in dungeon and treasure generation and description. Game prep becomes easier and pickup games convert many of their tedious pauses into time better spent exploring and roleplaying.
BTW, I first encountered Richard L. Blanc's blog just a few weeks ago, where he has at least fifty unique monsters both illustrated and statted up for 0e, B/X, and 1e. I look forward to his future products, such as the sandbox companion and the creature compendium.