The Art of Electronics by Paul Horowitx and Winfried Hill, especially sections 1.4, 2.2.1, and 7.1.3.
Engineer's Mini-Notebook: 555 Circuits by Forrest M. Mims, III
The Ultimate Beginner's Guide to the 555 Timer by Jesse Rutherford
The 555 Timer Applications Sourcebook by Howard Berlin
555 Circuits from Engineer's Garage