In one prison in New York, authorities tried to ban a book of maps of the moon, arguing that it could “present risks of escape”. In Florida, prisons have prevented inmates from reading Klingon dictionaries and a colouring book about chickens. In Texas, prisons have a banned list of more than 10,000 books by authors including Alice Walker, John Updike, George Orwell and Joyce Carol Oates.

With bookshops and libraries across the US marking Banned Books Week, an annual celebration of the right to read, a new paper from PEN America says that the largest ban in the US is in state and federal prisons, where more than 2.2 million people are currently incarcerated. The free-speech organisation is calling on the US Congress to convene immediate hearings on book-banning in prisons, with a petition signed by almost 40,000 people saying that Congress must “shed light on this critical right to read where it is being thwarted most severely”.

Describing the current restrictions on books in prisons as “arcane and arbitrary”, the petition says access to literature in American prisons is getting worse and worse, citing studies that show prisoners with access to outside information and ideas are less likely to reoffend.

Reasons given by prisons for banning books range from sexual or obscene content to depictions of violence or escape. PEN says that while these reasons may encompass areas of legitimate concern, they are often “construed so broadly that they essentially serve as convenient justifications for arbitrary bans … applied in ways that defy logic”.

The report notes: “Officials at one prison in Ohio prevented a book-donation group from sending a biology textbook to an incarcerated person, labelling the anatomical drawings as ‘nudity’ … Arizona has banned Dragonology: The Complete Book of Dragons, E=MC2: Simple Physics, and Sketching Basics. In Tennessee, officials refused to allow the literary not-for-profit Books Through Bars to send a book about the Holocaust to an incarcerated person, citing the fact that the book included a photo of the nude bodies of victims.”

At one federal prison in Colorado, officials stopped a prisoner receiving Barack Obama’s two memoirs, calling the books “potentially detrimental to national security”. This decision was later reversed.

PEN says that its report is not setting out to demonise prison officials or to “belittle legitimate security concerns”. But it does want to show that book restrictions in US prisons “are often overbroad, opaque, subject to little meaningful review, and overly dismissive of incarcerated people’s right to access literature behind bars”.

It continues: “The result is a book-banning system that fails incarcerated people, and fails to live up to our democratic and constitutional ideals. As both a practical and a moral matter, it is time to re-evaluate the state of the right to read within American prisons.”