onigoroshi:
I had a chance to check my library and the exact title of the Aagard book is "Excelling at Combinational Play". It has nice tactical exercises plus detailed explanations about them in the solutions area. Paata Garindashvili also wrote a good tactics book called "Imagination in Chess". Both of these should be in print and being published by Everyman and Batsford Presses should not be too hard to obtain. Being a library director, and an old reference librarian before going to the administrative level, it is always nice to be able to recommend books.

Yes and Colonel Crockett, just keep the play and study up. You are young enough and if you want that Master title you should obtain it. When I was in my early 20s it was one of my passions as well and I used to spend easily 3 or 4 hours a day on chess study, and more if you consider all the correspondence games. However I was the bookish sort and book study isn't necessarily the best way for chess improvement, although it suited my personality.