The Graded Go Problems for Beginners (http://www.amazon.com/Graded-Problems-Beginners-Beginner-Ele...) has four volumes of increasingly difficult tactical problems. For the strategic side of things, I enjoyed Janice Kim's Learn To Play Go series, which has five or more volumes (http://www.amazon.com/Learn-Play-Go-Masters-Ultimate/dp/1453...)

And, of course, with Go you have a nice progression from learning to play on the 9x9 board for tactics, the 13x13 board to begin learning strategy, and the 19x19 board to play the real game. And thanks to the handicapping system, you can play much stronger players with both of you playing your hardest and both with a chance to win.