Science book for 12 yr old?

Please recommend me a book! My little sister is turning 12, and this year I'd like to get her something she'll actually enjoy, so I was thinking a book about science of some sort. She likes geology, horses, and dogs, if those give you any ideas. ETA: Any non-fiction ideas? There are a lot of popular books about science out there, but it's hard to judge which would be most age-appropriate.

While we're at it, if you feel like suggesting a couple of historical novels set in England and/or France in the late 1700s (just before the French Revolution, preferably,) and a couple set in the late 1600s, (happy endings only, please,) I'd be much obliged.

Thanks!