The books are the textbooks that you'll wish that you would've had!
As such, the problems can be worked out with an exercise book - and, of course, may be handed down from son to son.
I'll echo the solutions manual recommendation - understanding that there are multiple routes to the solution is critical to gaining conceptual fluency (as opposed to procedural fluency) IMO. Additionally, the elegance and brevity of some of their solutions really helped my daughter to learn some good techniques for simplifying problems.
My DD started with pre-alg and has also done the first alg I class. We have taken a bit of a break due to other interests and activities but we expect to resume next February.
My DD loves AOPS and so do I because through itmy DD has learned some useful Maths and, even more importantly, persistence.
