Well I got a good score by using Barron's, Kaplan, and Princeton at the same time to prepare. They all have their pros and cons. Kaplans practice tests are too easy, but the test taking tips they provide are very effective. Barrons's tests tend to be harder than the real ACT but they have a very thorough review section. Princeton's tests are very accurate but the review sections lack content and depth. I recommend buying all three and going through all of them. I increased my score by four points in three months by doing that.