Here's just some pointers. I'll be torn down as some kind of anti-christ for my views, but they are just what I found. I'm coming to the end of my exams now so I've just gone through what you've been through.
1. Air Law
Do this first. I think that this is possibly the hardest exam to do. Just because everything is brand new, and you've never seen it before (or I hadn't). Learning the differences between height, altitude, level, aal, amsl, agl, transition layers is all a bit of a mind bender.
There's nothing else for it, but to just plough through it all.
2. Navigation
Next in line. I don't think you'll learn this from a book. You can do, but it will take for ever. You are going to need somebody to show you how to use the whizz wheel. You'll also need to practice every day. Unlike Law it's more of a pain to revise for because it takes so much longer to take each exam. Law is all multiple choice and you can just practice, practice, practice. Navigation requires significant calculations and so time is at a premium in this one.
Should be easier since some of the old concepts from law come up again and again. Invariably QNH, QFE, Transition layers etc will be asked about again.
3. Met
Like law, and again tricky because it's all new. I also found it dry and it's problematic because it's NOT a science at all. There seem to be fewer right and wrong answers. I also found it quite dull, but that was jsut me.
4. Radio Written
If you take this with some flight time (say 25+ hours) then it should be much easier. You will have heard or seen most of it before, you will have experienced most of it and so this is maybe the easiest one to do.
It's also on the way to Radio practical, if you are preparing for that, the written is MUCH simpler.
5. Radio Practical
You will need tuition for this, you can't learn it from a book. It's a toughie and it's practice, practice, practice with an instructor.
6. Flight planning
7. Human performance etc
Have yet to study these
Use
www.airquiz.com to practice your exams. Ask questions on here, but be aware these are not the most friendly forums on the internet and you just have to put up with being lampooned by some of the residents for asking newbie questions. Rest assured not everyone is like that though, so you should get some good replies.
Good luck. Taking the PPL exams is a significant commitment, but the feeling of accomplishment on each pass is a great feeling!