Im a 2nd yr DR...
n bought the phys books, but they r not essential...
One of the most important and useful books throughout your course would be
Bontrager n Lampignano's Radiographic Positioning and Techniques or something
Although its like $280 or somethin like that, i recommend buying it and Martini, cz these 2 will be the ones u can use to refer even after u r done wid ur course and stuff... quite useful ones
i got graham n cloke, and christensens phys books.. but they arent like u HAVE to buy them... u can always refer them from the library.
Gud luck!