I recently posted a link to part 1 of an interview with Boris Gelfand, and in that work he praised a number of books including the old, excellent The Best Move by Vlastimil Hort and Vlastimil Jansa. It's a book I had as a young expert and maybe went through one time. The book was long lost, but I picked up a used copy several years ago and decided to give it a gander on Gelfand's say-so.
It's an excellent work, based on positions from the two Vlastimils' games, which is itself useful as their games will be unfamiliar to almost everyone. (It probably shouldn't be so, at least in the case of Vlastimil Hort, who was one of the very best players in the world in his heyday, but that's how it is.) On the other hand, they were both great players and analysts, so the puzzles are of high quality. It's definitely worth picking up a copy if you can find one that's reasonably priced, though I'd warn players rated below 2000 that you'll be in for a lot of frustration. (One grows, in part, by persevering through challenges, but the challenges shouldn't be altogether out of one's grasp.)
Here's an early position in the book I was pleased to solve. (Don't worry, there's no progress from easiest to hardest; if this were one of the trivial puzzles the book would be impossible!) It's Black to move, and the assignment is to "[s]uggest the most aggressive continuation for Black."
The solution is here.