100 endgames you must know by GM De la Villa is a good book to study endgames.
Jesus de la Villa debunks the myth that endgame theory is complex and he teaches you to steer the game into a position you are familiar with. This book contains only those endgames that: show up most frequently are easy to learn contain ideas that are useful in more difficult ...
The following KNN v KPP endgame position is one:
Ply count=0. Black to play. White win without 50 move rule. Draw under 50 move rule.
This is the third position in the "two knights v pawn" section of Averbakh's "Knight Endings" (Batsford edition) where it gives a White win in 17 moves, but Black's defence can be improved.
Given that you are even asking this question, I am going to be a bit presumptuous and guess you are, like me, not a highly rated (elo > 2000) player.
For chess books that are not about opening theory, I would not worry too much about the age of the book. Sure, the occasional study or evaluation has been adjusted based on computer engines, but these are ...