I did a search in the forum but didn't find much,or something helpful.
Yeah the forum search might not be the best; google "best atpl books pprune" to read the countless threads on the topic...
I don't have time to attend a flight school.
You still need to be enrolled with an FTO to sign you off for the exams. The chances are the FTO would provide you with the material. If not, get literally anything other than the Oxford series. It's overly academic and full of outdated fluff. What they take ten pages to describe really takes one or two. They never explain why something is, just that it is. Some sections leave you even more confused than before. Jeppesen series are almost identical, in everything (style, structure, grammar). I seriously think the same people wrote it, or they copied each other.
Search for something that is written in a down-to-earth style with a lot of multimedia. Walls of dry text in 2016 won't cut it. Previous generations might have struggled to imagine how would a variable swash plate constant pressure pump work just from reading about it, today such concepts should be a breeze. Looking for something that would work for you shouldn't be too difficult; many publishers offer free samples. Those that don't would be happy (in my experience) to send you a free sample on request.