Yep, the two are not substitutes for each other. But analyzing all games you played, and when you read a book, trying to calculate yourself, instead of just skimming through the annotations are necessary to improve, imo.
"Chess Hero" (google it) is an excellent freeware that you can mix in playing and going through GM games, although not exactly, but to a good extent.

My Chess playing friend claims to study Chess strategy through books or old master’s games, and yet he is amazing and beats me every time (bar once – oh happy day).
Now, I believe it is important to study chess in as many variable ways as possible. I do not feel I could just play games and watch my rating grow. I read books, study master’s games, do some opening and endgame preparation, work on tactics to see the improvement through analyses etc.
After finding out my friend does not read, I have found myself feeling that the preparation I do to improve in not necessary.
What approaches do you have towards developing your own skills in Chess?
-Elona-