Get a copy (in book or CD Rom) form of the PPL Confuser (so called because it is not in the least confusing), which provides exam questions and answers with explanations (some of which are clearer than those found in standard textbooks such as the Thom seriers). You can use it as a primary teaching aid, and not just for revision, by working through the exam papers until you consistently get good results.
NB: I did the old CAA exams and so have no knowledge of the recently published JAA version of the Confuser but as I gather that the exams themselves have not changed dramatically I assume that the JAA version is OK. Also highly recommended for general reading: Stick and Rudder by Langewiesche and Flight Without Formulae by Kermode, both available on Amazon or from pilot shops.