You should be OK with 2004 books. The only thing which might have changed slightly is Air Law, which seems to change all the time.
However, if you're getting a set of Jeremy Pratt's books too, those will be up-to-date anyway.
Which is best, Trevor Thom or Jeremy Pratt? It's a matter of personal opinion, and if you do a search, you'll find plenty of those opinions on here! Basically, Jeremy Pratt is a bit more detailed and easy to read, and Trevor Thom more concise...so less pages to wade through! But people pass their exams every year with both, so it doesn't matter that much. And you'll have both, so see what you prefer.