I had come across Castle Oldskull before, and finally picked up The Classic Dungeon Design Guide (and many others) due to the sale.

This book has got to be my favorite of the bunch.

I am currently running though a random dungeon with this, using bits from the Guide and Traps books, solo with Scarlet Heroes rules and having a total blast!

Like someone else said this is much like a hyper version of the 4AD generation rules, with access to a lot more detail you might want for a full RPG. Should I survive/ever get bored of the dungeon I'll probably take the same hero through some city-state encounters and perhaps use the Adventure and World Generators to see where that takes me.

Kent David Kelly has done a great job with these books.