Dr. Wolf retired from dentistry at the age of 45 to pursue his lifelong fascination with WWII aviation history and outdoor pastimes of hiking, mountain climbing, road and mountain biking, and sea kayaking. He has authored over twenty-three books on WWII, including nine on American bombers, two on U.S. fighters, five on U.S. flying units, and three volumes on U.S. aerial armament. His personal WWII library, collected over 40-years, now contains over 25,000 + books and magazines; 10,000 + photographs; along with 2,000 reels of rare microfilm from original WWII sources; 1,000 + CDs of scanned manuals and books; and over 800 DVDs.