I took the TEAS on the 16th and ALL you need is the ATI book and the online practice test! So in answer to your question, YES! It is absolutely worth it!
Study the book and the only reason to look at another book is if the ATI book doesn't explain something to your satisfaction. It truly is a review of stuff we all (should have) learned through 12th grade. Although I never had all that Science in my education (Florida Public Schools).
The real test is exactly like the online practice test! I think I even had a few of the exact questions from the practice test on my actual TEAS test.