Middlesex Library has 21 copies of Pro-Transgender Novel

Wondering if pro-transgender themes are being pushed in Middlesex Middle School after we reported that Advanced English 8th graders were recently assigned a gender fluidity book? Consider that there are 21 copies of the pro-transgender novel The Art of Being Normal by Lisa Williamson available to all students (ages 11-13) in the school library. This young adult fiction follows the story of two transgender teenagers with topics including hatred of sexual organs, chest binders, hormone blockers, underage drinking, sex, attempted rape, and irreversible gender reassignment surgery without any mention of the potential permanent physical side effects. Please see below for highlighted content.

For reference, there are 12 versions available in the MMS library for students of Harry Potter & the Sorcerer's Stone, the first book in a series that has sold over 500 million copies globally. There is one copy of Catcher in the Rye and three versions of A Wrinkle in Time, two novels most consider genre classics for this age group. Or looking to the ancient classics, there are only seven versions of Homer's Odyssey. (Source:  Darien Follett Destiny)

Why are there so many copies of a book that is clearly pushing controversial and potentially age inappropriate themes? What staff or administration member(s) decided this book and this quantity was appropriate for the MMS library? What is the demand from students for this book?