This book is terrible especially for the math section. The order of difficulty in this book is so erratic and random that it does not match the one used on the ACT.

Here is an example of a math problem found in this book:

13) (5 1/8) - (3 5/6) = ?
A) 1 7/24
B) 2 17/24
C) 1 1/2
D) 1 1/8
E) 1 7/24

Here is another bad math problem:
35) What base eight numeral corresponds to 90_(ten)?
A) 882_(eight)
B) 102_(eight)
C) 110_(eight)
D) 132_(eight)
E) 112_(eight)

I recommend the Offical Guide to the ACT with 3 full practice tests, which does not contain any errors as far as I am concerned.