One of the books I took on holidays with me was Wallace Wang's "Steal This File Sharing Book," just published by No Starch Press. It's a great, thorough, easy-to-read guide to all the different ways to acquire files over the Internet, from sharing by email and IRC to getting the most out of multiprotocol P2P tools to seeking out and using ratio-based leet warez boards.
This is unquestionably the best book on the subject that I've read. It strikes the perfect balance between factual -- "Here is what is available, here is the law, here is the means by which you can download, here is how to minimize your legal risk" -- and philosophical -- "Here is a breakdown of music industry sales, here is Harlan Ellison's opinion on bookwarez, here's what crackers have to say about zero-day warez trading, here's the dumbass laws that have been proposed to allow rights-holders to remotely shut down your computer via secret kill-switches, isn't that crazy?"
Wang is an accomplished tech writer and a stand-up comic, so Steal This File Sharing Book is both funny and lucid. It assumes almost no technical knowledge and it walks the reader through everything from file-compression protocols to anonymizing proxies to the notorious cross-stitch-pattern-trading underground.
If you want to figure out how to file-share safely, avoid spyware, not get busted, and learn about the morality and ethics as presented by all sides of the file-sharing debate, this is the book for you.