Sweet! An index for that book! Now I can pull out all the myriad notecards and post-it notes hanging out of mine!
I recall, waaaaay back in the day, Judges Guild had something like this, but more to the tune of just a few dozen pages. I had that ancient relic at my side back in the 1st ed days. I love this stuff! Just roll up something on the spot, jot down some notes on an index card, and by next session I have that on-the-fly encounter fully fleshed out and integrated seamlessly into the campaign. The only downside is, after a few times, you have to start rerolling a lot or filling in the already used entries in some of the tables (for NPC details, anyway).