I can't say the very last book I bought because the person it was bought for might see this. The book I bought before that was, I think, H.R. Giger: www HR Giger com. If it wasn't that, then it was Watchmen: The art of the film, and The art of Terminator Slavation. Not because either of those were good films, but because the books were going extremely cheap so I grabbed them.
[edit] I came a hairs width away from buying a book of Gil Elvgren art last week, but I was buying pressies for others and forced myself not to get it.