I haven't seen the O'Sullivan study guide so can't comment on that. I did look at a rather old (1999) book called Preparing for the Physical Therapist Licensure Examination by Patricia Rae Evans, which was for the US exam, and it scared the pants off me, but some of that was the different terminology used etc... I get the impression that the US exam is harder than the Canada one??
I did read through Electrotherapy Exlpained (Principles and practice) by Low and Reed. and a book on Neurological Physiotherapy which I have lent to a friend and now cannot remember what the title was! Another Canadian PT also gave me Frank Pierson's Principles and Techiques of Patient Care, which they use (fairly basic stuff) and also "Musculoskeletal Assessment" by Hazel M. Clarkson.
Really I'd say just revise everything. I don't know how long you have been qualified or what your weak areas are, but just concentrate on areas where you maybe have not worked so much or so recently. Memorise things like normal ranges eg in respiratory, and lots of tests for everything msk.
As I said before, the test is entry level, and your own training will have been deemed to be roughly equivalent, so you should not have a real problem. Look at the example questions, they may well arise in the real exam.