Just about anything by James Patterson. They're all like 400 or so pages, super easy to read, and hard to put down. Any of his books in the Cross series are good, and in the last couple weeks I also read his books Sail, The Jester, and The Lake House, which were all good. Basically, James Patterson is awesome.
Door to december by Dean Koontz is an amazing book. although its fiction, the concept and central plot are extrememly interesting, and had me thinking hard about the power of the human mind. I highly highly recomend it, its a real page turner and incrdibly developed