Man, I'm more of an ETO kind of guy.
Actually, most of what I learned about the PTO was from a Time/Life book on the Pacific theatre that my school library had.
Cornelius Ryan was mostly an ETO expert, but maybe he wrote something? There also used to be a whole series of small trade paperbacks that went into some depth on specific WWII topics, but of course I forget the publisher or the name of the series.
Could I be any less helpful?