This page lists the works of at least two authors:
1) John Herschel Glenn Jr. (b. 1921) , astronaut and US Senator from Ohio. He wrote the foreword for Fitness Over Fifty.
2)John Glenn (b. 1963), author of The Soviet legacy in Central Asia
3) John K. Glenn wrote Framing Democracy.
4) John A. Glenn wrote A Dictionary of Mathematics.
5) Glenn, John. Catalogue of the Francis Trigge Chained Library, St. Wulfram's Church, Grantham
6) John Glenn cowrote the screenplay for Eagle Eye