Having recently passed my air law, I would agree with everything else already said. B U T...... In my opinion stay away from the Jeremy Pratt books. True the Trevor Thom are a lot more detailed, and so I chose Pratt, and during the exam felt like one. There were at least three questions that I had to guess at as there was no mention of the topic in the book I had spent 6 months reading. (eg, what should the aircraft identification plate in the cockpit be made of?) The answer is "Fireproof metal", but if I didn't work in aviation engineering, I would have been stuffed.
Thom is a lot more heavy going, but better, and leaves no doubt about the topic.
Good luck!!