The author of a best-selling book about his imprisonment at Guantánamo may be freed. Mohamedou Ould Slahi is a Mauritanian citizen and the author of “Guantánamo Diary.” Slahi has been imprisoned at Guantánamo for nearly 14 years without being charged with a crime. The prison’s review board has now declared he is no longer a “continuing significant threat to the security of the United States.” Ould’s review took place last week, but the decision was announced yesterday. Seventy-seven prisoners remain at Guantánamo Bay, nearly eight years after President Obama first moved to close the prison.