There's one version of D&D that often gets overlooked in the Edition Wars, even more so than AD&D Second Edition. This, in my mind, is a good thing. I've never heard anybody criticize the D&D Rules Cyclopedia over Thac0, rules bloat, or any other accusations as to why or why not this version of D&D is somehow inferior or superior. Instead, in my experience, gamers look upon the D&D Rules Cyclopedia with a certain amount of fondness.
It's not hard to see why.
Finally, in 1991, all of the rules from D&D booklets (Basic, Expert, Companion, Masters, and Immortals) were compiled into one book. Here you have a complete game, none of this splitting the game into 3 core books (PHB, DMG, & MM). You can use this book to take your character from level 1 to level 36.
(Though I've always kind of wondered: why level 36? Why not 30? or 40?)
Yet back in the day my teenage self turned his nose up at this game. Somewhere I'd read that D&D was meant more for kids younger than me. Besides, I played the Advanced version of the game, and therefore I was somehow special, superior. Ah, the wonders of teen angst...
I missed out on basic rules for mass combat and sieges, more detailed rules on weapon mastery, 10 second combat rounds, rules for stronghold construction, and introductory material and colorful maps for a campaign setting (Mystara).
Where was all of this in the 2e core books?
They weren't. Not really, anyway. 2e still used minute combat rounds. And all of that other stuff could be found in rules supplements. AD&D 2e had no "default" campaign setting.
But all of this stuff was in the Rules Cyclopedia, decently organized, on top of rules for character creation, spells, and a whole chapter full of monsters....all in a 300 page book!
With all of that material is should come as no surprise that the artwork inside is rather sparse, and I wouldn't say all that inspiring. Still, the Jeff Easley painting on the cover is pretty inspiring.
Even though the book is more than 20 years old, you can still find content to use in your old school games. Want to differentiate between the combat uses of various polearms? There's a list on page 81. What about hitting somebody with a black jack? That's covered in the equipment section. Need rules for siege weapons? That's also in the equipment section.
There's a lot in this book. Perhaps too much for a beginner. As I recall, the 1991 Dungeon & Dragons Game boxed set was meant for beginners (back in the day of boxed sets with lots of goodies inside). But the book itself is all organized and straightforward--there's just a lot of stuff to read through. Use the index.
Presentation: 8 out of 10
Creativity: 8 out of 10 (there's monsters here that weren't in AD&D 2e)
Utility: 7 out of 10 (again, use the index)
Get this if... You want a complete RPG in one book, or if you want all of the BECMI rules in one place. Or, get it for nostaglia purposes, or if you need basic rules for mass combat, stronghold building, and so on for your old school game.
Don't get this if... You're not interested in an RPG that's 22+ years old, or if don't like combat tables, Thac0, or both. (The D&D Rules Cyclopedia gives you the option of using one or the other).