This book is a great test preparation tool and a great general reference to have anyway. Its full of specific equations and succinct theoretical explanations.
I have yet to take the PE exam, but when I took the FE exam I remember crushing it because I had studied the reference material itself. I didnt do any practice problems, just brush up on what equations are used when and reminded myself of some obscure material. You are allowed to use the book during the exam, so familiarizing yourself with it before hand is essential.
Available here: Mechanical Engineering Reference Manual for the PE Exam On Amazon: