Every year, people request certain books be restricted or outright banned from libraries. Sometimes it has to do with content readers deem inappropriate. Other times, it has something to do with the author.
This year, the American Library Association says 323 challenges were reported to its Office for Intellectual Freedom.
According to that data, these were the most-challenged books last year:
1. This One Summer
This award-winning graphic novel by Mariko Tamaki got a lot of criticism last year. It was pulled from several school library shelves, including Minnesota's Henning School District.
The School Library Journal says it's about a girl who "spends a life-changing summer with her close friend Windy, trying to make sense of everything from parental woes to the drama of older teenage acquaintances."
However, it contains LGBT characters and addresses some sticky topics like unplanned pregnancy, the use of drugs and alcohol, vulgar language, suicide and sex. It's meant for kids 13 and up.
This is another award-winning graphic novel. Raina Telgemeier's book is about drama that happens within a middle school drama department.
It's meant for kids ages 10 to 14, and it drew controversy because of LGBT characters that weren't revealed until well into the book.
Read the description of Alex Gino's children's novel and it directly explains it's about a transgender child. The ALA says some schools got rid of the book because its content was deemed inappropriate at elementary school levels.
The book is meant for kids in fourth through sixth grades.
4. I am Jazz
The book has been criticized because it's a preschool to third grade level book, and it talks about what it's like to be a transgender child.
5. Two Boys Kissing
David Levithan's novel is for a slightly older audience: young adults or seventh grade and up. It's about two teenage boys who set out to break a world record for the longest kiss.
It's been criticized for its cover, which is an image of two boys kissing as well as its LGBT content.
The other books include John Green's Looking for Alaska, Matt Fraction's Big Hard Sex Criminals, Chuck Palahniuk's Make Something Up: Stories You Can't Unread, Bill Cosby's Little Bill Books series, and Rainbow Rowell's Eleanor & Park.
You can read more about all these books on page 16 of the ALA's report.
More about book challenges
The ALA notes that more books are likely challenged than it knows about. In fact, it estimates as much as 90 percent of book challenges are not reported to its office.
The study says concerned parents and other patrons make up 73 percent of book complaints. And the biggest complaint libraries get is about "sexually explicit" content in children's and young adult books.
Out of the hundreds of challenges the ALA records every year, about 10 percent are removed from library shelves.
In a separate study, the School Library Journal reported that more than 90 percent of elementary and middle school librarians have chosen not to purchase a book for the school specifically because it contains controversial topics.
More than 70 percent of high school librarians reported the same.