Ace the Tech Interview, I think, is an excellent little book. OK, it has a few errrs in it. Topics are wide ranging, answers are short and to the point and it has pictures
I have also kept my old ATPL theory books (BGS in my case) and find them to be an excellent source of reference. I'm sure you can pick up a set of the Oxford, CATS (or any other) books on e-bay for a few quid....... orjust ask in the Tech Log forum