Originally Posted by
Gertrude the Wombat
Air Law changes every five minutes.
Most of the other subjects remain the same for decades, because the physics and technology don't change - the air still behaves the same way, the aircraft still fly the same way, the instruments don't change (well, they do actually, but you learn the old ones for the PPL, if you want to do the fancy glass cockpit stuff that's usually after you've got the PPL).
+1
The only other but that I think has changed is Communications - but for this its best to ignore what it says in the book and look at the supplements to
CAP 413.
The later revisions of the others make minor changes and corrections - but aren't going to be fundamentally different.
Whether to go Pratt or Thom is a matter of opinion - I went Pratt as it was recommended to me by my instructor (and one fewer book makes it a tiny bit cheaper), but they are much of a muchness. Search the forum for opinions on both.