It really depends on what you want to get out of your ATPLs.
If you just want 14 passes at 75%, and then to move on, then skimming through the books and hitting the online question banks might get you through.
If you really want to understand the subjects, then hard study of the books is the only option. Particularly the more relevant subjects such as Instruments, and Airframe/systems.
There's a few pointless and fairly easy subjects in there, like Air Law, both comms papers and HPL. The databases alone should get you through these.
Most people need to work pretty hard at subjects like Gen Nav, lots of formula to learn and plenty of example calculations to go through. Really get to grips with your CRP-5.