Conn. (WTNH) — Book banning is a hot-button issue sweeping through the United States.

In most cases, these controversies are centered around censorship in schools and libraries. Many educational institutes in the U.S. have banned books discussing race, religion, gender identity, sexual orientation, and more. This trend has only spiked in the last few years.

But in the U.S. and in Connecticut as well, there are far more restrictive places when it comes to literature: prisons.

The Marshall Project, a self-proclaimed nonprofit and nonpartisan news organization, went state-by-state and assembled a list of banned books in each of their prison systems.

In Connecticut, about 1,660 books have been banned from state prisons. But why?

The Marshall Project’s list provides a range of answers as to why each specific book was banned. Some of the most frequent reasons are for containing sexually explicit content, content that may promote violence or criminal activity, and safety and security reasons.

The answer “safety and security reasons” is listed without any further explanation. And many titles are not given a reason for being banned.

Titles such as ‘Fifty Shades of Grey’, Pride & Prejudice’, and ‘Sports Illustrated’ are banned for containing sexually explicit content. The book ‘V for Vendetta’ is banned for safety and security reasons, and so is a book titled ‘Pimpology’, which is also banned for containing sexually explicit content.

The U.S. Army Manual was barred for “containing weapon construction procedures.”

Other items banned include a collection of poetry by Tupac Shakur, autobiographies from Ke$ha and Marilyn Manson, graphic novels from ‘The Game of Thrones’ series, a comprehensive book dissecting the cannabis industry, and much more.

To see a full list of every banned book in Connecticut prisons, click here.