Well, Jeremy Silman's Reassess Your Chess is a fantastic book for all areas of the game, and the best middlegame book I've cocme accross so far, as well as it being a classic, is Peter Romanovsky's Soviet Middlegame Technique. Absolutely fantastic book and it's undoubtebly a classic of Soviet chess.
I have Romanovsky's Chess Middlegame Planning. I don't know if that's a different version of the same book or a different book. I do know that I found it quite helpful when I worked through much of it ten years ago.
Hmm, I think Reassess your chess is a good book and a book that would be worth to try at least. I have read a lot of good things about it.
About how to beat your dad, well, I need to understand postional advantage and especially endgames, I think that if I am good at something, it is finding those kind of tactics (or at least I have that sense more developed than the others).