You could try "Buddhism" by Christmas Humphreys (founder of the Buddhist Society, London), published by Penguin. If your interest is more specifically in Zen Buddhism, I'd recommend, "An Introduction to Zen Buddhism" by Daisetz Teitaro Suzuki and "Way of Zen" by Alan Watts. All three books can be easily found and purchased online. Excellent online resources for Buddhism can be found at http://www.thebuddhistsociety.org.uk/
and http://www.buddhanet.net/
I'm currently reading The Idiots Guide to Buddhism and find it excellent. It's simple enough to understand but has enough detail to explain things more than just superficially. There are some bits that I still don't get but I can't put the book down just now.
First of all Buddhism is not to be studied really but to be practiced. To learn the art of Vipassana... the orignal meditation which Buddha used to become enlightned visit www.dhamma.org there are vipassnana centers around the world and instruction and living accomodations are FREE. You must however make a 10 day commitment. ITS WORTH IT! I tell you, that was one of the most importnat experiences in my life and I plan to go again.