I can only recommend Bristol as it is very comprehensive. The information though is very compressed compared to others ( jeppesen etc.) so you really need to read and study it thoroughly and a teacher in some subjects would be helpful (POF, RNAV and PERF just to name some). The highspeed flight section is difficult to understand without any classroom lesson and it lacks a questionaire after each subject at least on the paper files. However, there is a very good DVD(
AFAIK it comes with the paperstuff) with detailed animations and a very challenging question database. You shouldnt have any problems passing the exams if you are able to reach 85% in the Bristol GS tests.