I feel Jira Admin exam is not only about "how much you know Jira admin" but rather "the best way of doing Jira admin in different situations". I don't think the existing books (including mine) were written with a purpose of providing a guide to clear the exam. We are anyways not allowed to share sample questions asked :)
Each book is based on experiences of author when they were working as Jira Administrators. You will learn something different from each book. Comparing them is probably not a good idea.