General

Good Sherlock Holmes book?

I need to read any Sherlock Holmes book, that is not too short or not too long, for a class and I was looking for you basiler's opinions.
The only one I ever read was Study in Scarlet and that was a pretty good book, but I can't pick that one.

Thanks for any recommendation(s)
I know I should search for one in google or something, but I'd rather have one recommended than picking a random book