Best study books for Subject Tests

Which books do you recommend for Subject Tests?

You should get the official guides with 4 real tests. Barrons and Princeton Review are generally good, but it depends on the subject.

The Princeton Review’s was found to be excellent in the Maths part. It explains the concepts lucidly.

I have used Kaplan, and I found their tests were much harder than the actual SAT.

Is kaplan book useful