I found couple nice photos of GIs reading in the National Archives collection. It looks like the guy above is reading a Pocket Book paperback. Here's the original caption: Enlisted men at the transmitter pool of the signal section of the US Seventh Army in Germany, relax by reading and playing cards in the enlisted men's quarters. January 3, 1946. (I cropped out the guys playing cards)
Original caption: These men of the 3rd Constabulary Regiment are shown as they make use of a few of theor off-duty moments in the mobile library which is being used at their station until the new library is ready for use. The 3rd Constabulary Regiment is located in Wetzlar, Germany, where they are in training for occupational duties. April 24, 1946.