A few weeks ago I mentioned the puzzle book by Vlastimil Hort and Vlastimil Jansa, The Best Move. It is a fine old work (from 1980), rightly acclaimed and featuring a nice mix of positions to solve. Almost all of them are reasonably challenging, but their character differs: some focus on judgment, some on a deep tactical point, some involve little tricks, and so on. Even the way the tasks are posed is often clever, managing to perform that most difficult of tasks in a tactics book; namely, not giving away half the solution in the question.
Here's an interesting puzzle I came across a week or two ago, #60 in the book.
Here's the task:
Black to move.
1. Black is (a) better, (b) equal, (c) worse.
2. Black's best move is (a) 1...Bc8, (b) something else.
The solution is here.