The Practice Effect

The Practice Effect by David Brin, 1984, 277 pages
(9th grade up)

I haven't read this since college and I had fun reading it again. Dennis, a physicist, is trapped in an alternate universe where the laws of physics are different. In this universe, the more you use (or "practice") a tool, the better it becomes. If you don't use it for a couple of weeks, it will deteriorate. The same goes for clothing, vehicles, etc. Once Dennis realizes what is going on, he's able to use these laws in a way that appears magical to others. Yes, it's pretty unbelievable from a science perspective, but if you just take it as a really imaginative fantasy with some science thrown in, it's great.