The C.S.P.T. is not a license, but a certification.
I found these couple of books to be helpful, but compounding experience is what I believe to be the most crucial in test preparation:
Mosby's Sterile Compounding for Pharmacy Technicians: Principles and Practice
Sterile Products and Aseptic Techniques for the Pharmacy Technician by Mike Johnston
Also, there is an excellent course provided by N.P.T.A.: