The Shades of Grey series is the most popular reading material among Guantanamo detainees in Camp 7, a congressional delegation learned during a trip to the prison facility last week.

"Rather than the Quran, the book that is requested most by the [high-value detainees] is Fifty Shades of Grey. They've read the entire series in English, but we were willing to translate it," Rep. Jim Moran (D-VA) told the Huffington Post. "I guess there's not much going on, these guys are going nowhere, so what the hell."

Camp 7 holds 15 "high-value detainees," who military officials refuse to comment on.

The Guantanamo Bay prison facility still houses 166 detainees, though the Department of Defense has authorized two detainees to be transferred back to their home country of Algeria. Eight-six detainees have been cleared for release, but their fate remains unclear.

"Every day Guantanamo remains open, the reputation of the United States suffers and we provide anti-American propaganda to our enemies," Moran said in a statement last week. "Maintaining the detention center at Guantanamo Bay is more about politics than good policy. It is not worth the damage it continues to inflict on our international standing, including our ability to stand up to human rights abuses in other countries.

"I applaud the President’s commitment to closing this facility and will continue pursuing all legislative options that will allow for the transfer of the remaining 84 detainees who have been cleared," he concluded.