dear john,
its not possible to give you a sure shot idea for the books as every topic ask a different book for his need.
For a comprehensive study i prefer
low & reed-electrotherapy(england edition)
claytons-electrotherapy
some relevent books of indian edition in orthopaedics,physiotherapy in surgical contions,massage,bio mechanics,pharmacology etc.
kisner kolbey-exercise therapy(ohio edition)
dena gardiener-exercise therapy
medicine-davidson
EXAM PREPARATION GUIDE BOOK OF O'SULLIVAN