High school teachers always have goodies awaiting them in their school mailboxes. Many of these treasures are commercial solicitations, and some of them are useful.
One solicitation I can count on year-in and year-out is for D&S Marketing's AP Physics Exam prep book. The book is essentially three practice multiple choice tests. So far, so good. There is a market for such a book, and I'm in it.
One problem D&S faces is copyright infringement. The sad reality of the school market is that teachers will buy a single copy of such a book and blast out "unregistered" copies using the school's photocopying technology. D&S maneuvers around this by selling their book in packs of 10 or more. If you want one copy, you'll have to buy ten. No quibbles there.
I do have quibbles elsewhere.
Probably the least of which is that I already have every product they've ever pitched to me. I have the first and second editions of their AP Physics prep books. I'm not likely to buy any more of the second edition, so the year-in, year-out marketing barrage is wasted on me.
I will probably also pass on future editions. The first edition was fairly good. The trick to these publications is to match the coverage, depth, and difficulty of the actual College Board Advanced Placement Exam in Physics. No mean feat. The first edition came close, though the item writer clearly had some favorite topics that strayed from those of the College Board's syllabus.
The second edition, however, was over the top. Each item was an exam in itself. Much harder than the actual AP Physics Exam. For me, the second edition was of no use. Your mileage may vary.
The best bet is to collect all the released items you can from The College Board/ETS. I've been able to collect released items from the 1984, 1988, 1993, 1998, and 2004 exams in my long and storied career. Those items will always be better than anything offered elsewhere.