For years I was of the opinion that the D&D Rules Encyclopedia was the best everything-you-need-in-one-book version of the game ever produced by TSR. It has lots and lots of stuff: Classes beyond the BX 4+3 in both core and prestige varieties, rules for play up to 36th level, craploads of monsters, an optional skill system, weapon mastery rules, the War Engine mass combat system, maps of the Known World of Mystara, rules for becoming Immortal, etc, etc, forever and ever Ah-men.
But at some point I turned a corner on wanting all that stuff spelled out for me. Nowadays I think Dr. Holmes's rulebook is the shiniest one-book approach to D&D that TSR put out. Why? Because it is woefully incomplete. There's just enough D&D there to play some D&D and hardly anything more. The rest of it is on the DM. How do the gods work? What does the world look like? How do I run a whole war? I'm not sure I want my D&D corebook answering those questions for me anymore. The Rules Cyclopedia is still a great book. I'd call it a star in the crown of TSR. But I'm pretty sure it's way more D&D than I'll ever need.
"Man, is there anything Jeff CAN'T do when it comes to gaming? This guy is like a critical 20 every roll. Jeff can bite the heads offa five game geeks, including their sorry-ass DM, and spit 'em into a large duffel bag ONE AT A TIME!...that's just the kind of messed up bastard he is! You think yer a gamer, punk? Well..do ya? Jeff will depants your weasel-ass right in front of your grandma."