Abebooks.com, now owned by Amazon.com, is a great place to buy older, used books. I’ve been buying some technical books at $1.00 a piece. For any current in-print books, Amazon remains the only place to buy after Quebecor has bought and closed Camelot book store.
The AP Stylebook is recommended if you want to write good (American) English. It tells you when to hyphenate, to spell the numbers and to choose the correct word. What is the difference between assassination, homicide, manslaughter and murder? The AP Stylebook will tell you. The Ask the Editor section on their website is very helpful too.