Sure, it was Don't Make Me Think by Steve Krug. Quite good, although just a basic short intro book on web usability. I'm generally hopeless at design, so it's given me quite a few ideas. Namely remove 80% of the wall of text on my site!

I've also picked up The Design of Everyday Things by Donald A. Norman. Haven't got around to reading it yet as it's not about the web, more just everyday design and usability, but it came highly recommended.