Not really a study guide. More of a practice test.
I purchased this book to help me study for certification in microbiology.  I found that it is just a bunch of practice questions.  The practice questions are great as a way to see what the test will be like, but not good for finding all the info needed to study.  I recently purchased Microcards: Review Cards for Medical Students and Clinical Microbiology Made Ridiculously Simple.  Both are great tools for studying.
This is the only quiz book available in the US because it relies strictly on non-fictional facts about Potter and Rowling, and therefore does not infringe on Rowling's copyright.