there is so much to read about propagation, no single book (or web) could cover it.
I reccomend you start with a Google search, to get a feel for the modes available.
I suspect your main interest is in H.F. propagation at the moment.
Several books are also useful for quick reference, the RSGB, ARRL and almost every radio society have exellent material available.
Rallies are a good place to go book hunting, often secondhand, no matter how old they are, the information will still be valid.
Failing that, borrow some from the local radio club (or members), the RSGB yearbook has a section on propagation, which most clubs have.
Try the local library! you may be suprised what you find!