Okay, I'll be honest. LISP scares the dickens out of me. It's ancient by the standards of computer languages. The language is completely different from any of the stuff I use in my day-to-day programming. Yet it has all the features of those languages and more. Garbage collection? Got it. The ability to pass functions around as easily as an integer? Done (and not in a cranky C function pointer manner, either). Object-oriented programming? Well sure, but you might not need it as much as you thought you did. Not only that - LISP has had these features for decades.
Paul Graham is a high-profile proponent of LISP. He seems to think that his early success in developing online applications was due to the power and flexibility of LISP and his theory that independent-minded hackers are innately destined for greater things than the mundane cattle that walk the earth. I'm not going to argue with him, since I'm not a master of LISP, business management, or socio-economic theory. I do wish he'd find something more interesting to talk about than hackers, though.
Sorry, I digressed. As I was saying: Paul Graham is a high-profile proponent of LISP. His book ANSI Common LISP is on the bookshelf of nearly every would-be LISP hacker, and for good reason. His book is concise and informative. It continues to be useful after finishing the tutorial section, thanks to a convenient reference section in the back. You'll probably get some respect from your fellow nerds if you have any of Paul Graham's LISP titles on your shelf. That includes those who get bored and annoyed while reading his essays discussing how the ancient Egyptians who designed the pyramids were actually hackers who utilized the existing labor system in previously unimagined ways. Note: I don't think he's actually written that essay yet.
ANSI Common LISP is popular and useful, but I needed a friendlier approach to learning this intimidating language. That's why I preferred Practical Common LISP by Peter Seibel. It takes a more leisurely stroll through the awkward first steps with LISP. The author understands the widespread fear of LISP and takes it into account through each lesson and project. You will definitely have an understanding of the language and its possible uses by the time you're finished. I highly recommend Practical Common LISP for your first book as a Smug Lisp Weenie. Then go right into Paul Graham's books or some of the arcane titles that come out of the MIT Press with titles that are sure to impress your friends and frighten the neighbors.