My very favorite go-to reference book is Complete Guide to Quilting by Better Homes & Gardens. It is available on Amazon for $13.50. I bought one for my SIL and read it so much I had to get her an "unused" copy. My DD is just getting interested in quilting and she borrowed it two weeks ago. I wanted it the other day to check a technique. Guess I'll need to get her a copy of her own!
It's OK if You Sit on My Quilts is another interesting book for learning about block and pattern construction.