I would say at this stage you would be wasting your time doing the ATPL stuff.
If you want to learn the basics very good, at a level above PPL, then get hold of a set of the Oxford PPL books. They will get you well prepared to start the ATPL.
Because the basic foundation will be in proper and serious PPL study. I have seen/used a couple of the AFE books for PPL, and I found them very poor, and boring.
First you need to understand and learn the basic concepts, and you will not learn that in ATPL, until you have done your PPL properly.
The subject you should study to death at PPL level is Principles of Flight and Meteorology, as these lay the most crucial foundation for your safe PPL flight, and the POF will give you good understanding for what will come when you start on the ATPL.
The Oxford PPL books, are much more extensive then PPL level, at the same time they are not so tiring to read. Advice, reading the ATPL books now would be a total waste of time for you, as you haven't done your PPL.
You got to learn to walk before you can run, or?
Anyhow best of luck.