Well, you'll probably get plenty of reading material at the course, however, assuming your starting at the beginning, the General Dynamics books are always a safe bet, and they're relatively inexpensive.
How is your maths? People stumble on theoretical UT course work generally on the maths - three areas in particular. Trigonometry (sin, cos, tan) to work out refracted angles, scientific notation of large or small numbers for wavelengths (you will be dealing with millions of cycles per second, thousands of metres per second and thousandths of metres) and transposition of formulae, if x = y/z, then z = y/x. If your math is OK then you'll be adept at using these three. If not, then work on them so that your course time can be spent learning ultrasonic theory and not maths.
A book I believe should be required reading for all materials, welding and inspection personnel is J E Gordon's "New Science of Strong Materials" which is so well-written that after reading a layman can sensibly discuss fracture mechanics and crack growth. Specifically for the UT tech is J.C Drury's "Ultrasonic Flaw Detection for Technicians" available from the BINDT.
Enjoy your course!