After you've finished Card-Play Technique, this comes next. I have a huge collection of bridge books, but hardly any past about 1970. For some reason nobody has been able to write books of the standard of those early English writers: Mollo, Simon, Reese etc. Their insights are never going to lose their relevance and they are written exquisitely.
Both Mollo and Skid Simon could have (and, in the case of Skid, did) write about anything and been successful. Reese, however, is more like an expert's expert. He's another one of those writers who talks about the basics in a way that takes you back to him when you feel you have lost your way.