Hello!
 
I don’t know of any free online versions of the textbook because the book is specially made for UMich, but there are a few listings on facebook if you are interested in getting a cheaper copy of the textbook.
 
The textbook is very useful for giving detailed explanations of topics presented in class and multiple practice problems that test your understanding. Although the book is good for understanding the basic underlying concepts, I did not find it super useful for preparing for exams. Doing the provided practice exams are a better way to prepare yourself for the actual exams, as opposed to the practice problems in the textbook.
 
Hope you found this response helpful!
 
Best,
Caitlin, PMH Advisor