[FEN ""] 1.e4 e5 2. Nf3 Nc6 3. Bb5 a6 4.Bxc6
Is there a good opening repertoire book for White advocating the Ruy Lopez exchange variation?
Larry Kaufman's The Chess Advantage in Black and White is a well-regarded (though old, by opening book standards) repertoire book that uses the Ruy Lopez exchange.
I had also problems with finding good book about it. What is worth Chessbase has videos tutorial about it and I find it quite resourceful.