My copy came from my father as well - very humorous cartoons and interesting narrative. Though some of his cartoons predated, most Willie and Joe cartoons were printed in the
Stars and Stripes soldiers paper. Have to believe Mauldin made quite a contribution to the soldier's morale. Perhaps unsuprisingly, General George S. Patton called him an "unpatriotic anarchist" for his cartoons as they didn't show appropriate levels of 'spit and polish'. Patton wanted to ban
Stars and Stripes from his command, but General Eisenhower instructed Patton to leave Mauldin alone; he felt the cartoons gave the soldiers an outlet for their frustrations. "
Stars and Stripes is the soldiers' paper," he told him, "and we won't interfere."
In addition to 'Up Front' there is this compendium:
https://www.amazon.com/dp/B002DMJTZA/?tag=civilwartalkc-20