Since some others mentioned going back through their history at amazon, I decided to take a peek at mine. It took some digging, as I had to recall what email address I was using when I started out. My first purchase:
December 26, 1996 – 1:47 PM PST
Creating Killer Web Sites – D. Siegel
Looking back, it wasn’t that bad of a book at the time. No one was really pushing design boundries until Siegel came along with his giant images, lack of alt text, and single pixel gifs. We’re still paying the price of his suggestions, but they were in hindsight, not entirely a bad thing.