Accuracy of ACT Prep- Book Questions

Hello,
So, I have a question that seems fairly reasonable for someone to answer if they already took the ACT. I’m a junior and I’m taking it for the first time this Saturday (although I’m planning to probably take it twice more). I’ve always been a really good student, above the 90th percentile in my state for every subject except math, which is in the high 80s range. I’ve been told by English teachers that I’m a great writer and I excel at grammar. (The English portion of the test will most likely be my highest score.) Here’s the problem: I bought a prep book for the ACT a few weeks ago, and I’ve been completing practice problems on ACT’s website, and I’ve been doing terribly! I don’t understand…I’ve always been a good reader, but I literally got half wrong on the last reading practice test I did (it was only 10 questions…) And it’s not like I’m a bad test taker. I’ve always done really well on state standardized testing every year. Really well. My PSAT score was not satisfactory in my opinion, but that’s one bad test out of all the “big tests” I’ve taken in high school. I mean, I usually do really well on final exams, I got a 4 on my AP test sophomore year, I have nearly a 4.0…
Here’s the big question: are the prep book questions similar to the questions you see on the actual test? Basically, did you take the test and think it was a little easier than all the prep books made it out to be? That’s my question. I’ve heard a lot of people say that obviously prep books are going to put harder questions in there, because they want to prepare you as well as possible. I really, really hope that’s true.
Anyone take the ACT and think it was easier than the prep books made it seem? THANK YOU.

The best way to study for the ACT is to practice with REAL ACT tests. There are 5 tests in the Red ACT Book, 3rd Edition. ACT released several tests in booklet form.

Time each practice session to simulate the real test.

English 75 questions in 45 min.
Math 60 questions in 60 min.
Reading 40 questions in 35 min.
Science 40 questions in 35 min

Score your test and review only what you got wrong after each practice session.

I suggest the following schedule:

Take 1 section each school night/with review for 4 nights/week.
Twice per month on a Saturday or Sunday take a full ACT test/with review.