When Goren and Eames leave they give Arnie a hardcover book to read. But only paperback books are allowed in prisons. Hard cover book boards can be turned into crude knives (shanks) by prisoners, so they are banned by law.
Re: hardcover book in Jail. Here is the actual rule as per the New York corrections website.
"Detainees may receive one cubic foot (12 inches X 12 inches X 12 inches) of non-legal printed materials, including soft and hardcover books, magazines, newspapers, periodicals, pamphlets, advertisements and other printed articles, in any combination."