I have been tutoring kids in ACT and SAT and used this book for beginning the ACT process. It is definitely easier to get a 33-34 on this test than on the real thing but you can resolve a lot of timing issues and get familiar with the format with this. After some point the student using these tests the student should be pretty good (31-35 on these) and then it is time to go to the real thing with "The Real ACT Prep Guide" or some of the sample tests from the ACT web site. There will be a drop of about 5-10 points in scores but the timing and format issues will be resolved and the confidence has risen from seeing the improvement in the "made up" tests here. These are important issues and worth the investment in time and money since the real tests are in short supply.
The science questions are easier in that the real test often requires looking at relationships between two charts, or a table and a chart, where this book only asks for interpreting one table, passage or chart at a time. Many people have trouble reading tables or graphs so getting familiar with them is a good thing.
What I do is go over every error with the student that they made on the sample test, make sure there is complete understanding, make up some similar math problems, or similar questions related to the reading or science passage, and show what the underlying method is to answering this sort of question.
There is no reason to need a tutor like me if the student can fully understand most of the answers to the tests, stay on schedule (like doing a test a week or whatever time allows), make up (or find) similar problems to get practice and figure out the short cuts. That many people cannot do all of the above is what keeps the tutoring field alive.
The reason for 4 stars instead of 5 is the tests are too easy, and there seem to be about 1-2 errors on each test which is not enough to worry about. So use this book, keep to a schedule, go to the real ACT book when you have a good score on these, and make sure you understand the answers.