Handbook of Applied Cryptography, 5th Printing, http://www.cacr.math.uwaterloo.ca/hac/

Each chapter is available in pdf.

Just finished From a Buick 8 by Stephen King a few days ago and at the end of the book King recommended reading K.C. Constantine's books. So, this journal entry to remind me that books by K.C. Constantine might be something to look into if I ever finish reading the many books I already own.