Due to the fact that Astrophysics is a vastly broad subject, I would recommend that you start by one of the following books.
An Introduction to Modern Astrophysics by Carroll and Ostlie
or
Astrophysics for Physicists by Choudhuri
The first one is the considered the standard textbook in numerours astrophysics courses and the later one is one that I found particularly good.
The "Foundations of Astrophysics" by Barbara Ryden and Bradley M. Peterson. recommended by George Jones is also pretty good, although I believe that Ryden did a better job with her Cosmology book.
On the other hand, the Cosmology book by Harrison, is an excellent introductory text for cosmology, but I don't think that it covers much of the general astrophysics topics that one would like to learn.
In case you would like learn more about more specialized topics such as star formation, fluid dynamics... there are a lot of textbooks especially written for that.