In my personal collection are:

Fluid-dynamic Drag by Hoerner $$$
Aircraft Structures by Peery $$$
Aircraft Structures by Bruhn $$$$
Airframe Structural Design by Niu $$
Aircraft Performance Stability & Control by Perkins & Hage $$
Aircraft Design (vol. 1 - 8) by Roskam $$$$
Theory of Wing Sections by Abbott & Von Doenhoff $

....which is more than enough info to design just about anything.

But some of my non-technical favorites include "The Great Book of WWII Airplanes" and a bunch of stuff by Bill Gunston (who has written over 350 books!).