Nothing wrong with reading up on the subjects that you will encounter during the ATPL theory exams. Just be careful that you don't get too carried away with the details. Whichever school you decide to use in the end for your training will most likely produce their own manuals, and these may disagree to some extent with what you are currently reading, or have a different emphasis on the subject, or a different approach to teaching it.
Having too much advance knowledge of the subject can, believe it or not, be a distinct disadvantage for the ATPL exams. The JAA do not require an in-depth understanding of each subject, simply the ability to recognise the correct (or most correct) answer from a choice of 4. Often this only requires the most rudimentary understanding of the basics. A number of my colleagues during groundschool had degrees in physics or aeronautical engineering, and knew that the basic, over-simplified explanations sufficient for the JAA were in fact quite incorrect in a strictly scientific sense. They therefore found it difficult to ignore their own knowledge and accept the 'correct' answers required by the JAA.
Your most valuable asset though, would be to use your time now to try and gain as full an understanding as you can of how the airline business actually operates. You are extremely unlikely to get sponsorship (the odds are quite literally thousands to one), just as you are also extremely unlikely to end up with a major carrier. Research what other options are open to you once you finally get that CPL, as this is where you will probably end up post-training.
Go into this business with your eyes wide open, rather than a head full of dreams. Whilst you will undoubtedly enjoy the experience anyway, it is best to avoid focussing too strongly on a very narrow set of options, as failure to attain these may cause a great deal of disappointment. Speaking as someone who has had a rather large and unexpected spanner thrown into the works of my flying ambitions not once but twice, I hope you will take some well-meant advice to broaden your career horizon.