He has written over 20 books, including Pinstripe Empire: The New York Yankees from Before the Babe to After the Boss and Casey Stengel: Baseball’s Greatest Character.

[4][6] Appel began his career in baseball while a student, after writing to then-New York Yankees public relations chief Bob Fishel.

[4][7] Appel began his tenure with the Yankees in 1968 at age 19, handling fan mail for Mickey Mantle.

[12][13] After resigning in early 1977, and starting a sports management company, Appel handled public relations for the New York Apples of World Team Tennis, a team featuring Billie Jean King and Vitas Gerulaitis.

[11] In addition, Appel worked for the Atlanta Committee for the Olympic Games, The Topps Company, and assisted in handling public relations for the Israel national baseball team in the 2013 World Baseball Classic – Qualifier 1.

[16] In 2007, Appel led the public relations efforts for the short-lived Israel Baseball League which debuted and shut down that same year.

[8] While serving as VP for Public Relations for New York City television station WPIX, Appel won an Emmy Award as the executive producer of Yankee telecasts, a position he held for 11 years until 1992.

[23] He has contributed to publications including Sports Collectors Digest, Yankees Magazine, and Encyclopedia Americana.