we have to take the hesi a total of 3 times during our program, at the end of 2nd, 3rd, and 4th semesters. it is set up to cover the material we have covered up to that point. so, it is customized by your program (from what i understand). our school rules are if you do not pass with an 85, you have to do remediation. i just took mine last friday and made an 85.88...whew!!! just barely passed. the test is graded very strangely (imo), but it has all the areas broken down and gives you grades on each system, medications, or other area, etc. with the graded sheet, you can look and see where you need to brush up on your knowledge base. you can get all questions correct in say the cardiac area, but the most you can make on that section is 99.99.
i did not study or review for the test. just went in, calmly sat down, took a deep breath, and plunged in. it took me just over an hour to complete. there is some study material available, i don't have the website handy, but type in a search for "hesi" and you shouldn't have any problems finding the official site.