The information in the ATPL notes that you get will be sufficient.
Don't add to your workload unnecessarily.
You will need to be concentrating on your PPL exams before you do your ATPLs so, I suggest that you purchase the PPL series by Jeremy Pratt, or the more traditional Trevor Thom series.
Or, if you have the extra cash, Transair pilot shop and Oxford Aviation have a series of PPL CDROMs that you can buy - bit pricey (what with OAT's name on it isn't!
)
You could also buy the Jeppesen Private Pilot's Manual which is FAA based but for my money will give you a great introduction into aerodynamics and the principles of flight and also since you will be learning to fly in the US, it covers US airspace and talking on the radio too!
Enjoy your training - your first solo will be the best day of your life! (unless you've slept with Avy Scott!)
Farrell