Greg taught in the Xenia (Ohio) Community Schools for 30 years, first as a music teacher and later as a librarian. He became the Curriculum Materials Center Librarian at Cedarville University's Centennial Library in the fall of 2002 and served in that role until July 2012, when he became the Digital Commons Director. He is active in music, serving as the organist at his church, having sung in the Bach Society of Dayton and in Coventry Green, and serving as bagpipe tutor for beginning students of the Miami Valley Pipes and Drums. He has also been a reviewer of children's and young adult literature for Library Media Connection magazine and has served the Association of Christian Librarians as Chair of the ACL Award for Excellence in Nonfiction book award committee. Professor Martin retired in 2023.