Book recommendations?

I'm looking for book recommendations! In particular, I'd like to read some nonfiction, preferably popular science. 20-30 years ago, I used to read Stephen Jay Gould and Oliver Sacks, and I quite enjoyed the non-academic but still informative style. The weather should be sufficiently not-bad this weekend that I can make it to the library by bike, but I need to request books now if I want them to be waiting for me when I get there.

Specific genres of interest, in order of preference:

* Popular science
* Other nonfiction of the "more readable than dense" sort
* Fantasy & sf (preferably small stories in pleasant settings; ie, not dystopian or grim)
* Romance (gay, straight, poly, I don't much care. I have read tons of this lately and probably won't read any new recs right away, but I'm always looking.)

Thanks!