I just took the HESI yesterday...ended up with a 93.41% overall and an 850 on Critical thinking.
I didn't have to take any Science portion though so if you DO have to take the science portion then that would be someone else specialty.
I HIGHLY recommend getting the Evolve Reach Admission Assessment review book, I got if from Amazon
for around 30$ (that will cover EVERYTHING but Critical Thinking) Some of the questions in that book were even on the test so its definitely worth the money and gives you a lot of info. The vocab in the book isn't the best for the test but if you can find any Medical Terminology
book, it would definitely come in handy!
As for the critical thinking section i would HIGHLY recommend Fundamentals Success (a course review applying critical thinking to test taking) by Patricia M. Nugent and Barbara Vitale. This book also has two dvd's on it that not only help with nursing course review but also the NCLEX test review! so its a book you can keep throughout your nursing school career! I got it for 28$ from Amazon and it is nothing but tons of questions involving treating patients as a nurse. Some of the questions I seen in the book were also on the test!
Other then that, don't worry too much about the test, it really was not as hard as some people make it out to be. but those 2 study guides helped me TREMENDOUSLY! so good luck and I can answer more specific questions if you need them!