E. E. Smith 
First Lensman [EPUB ebook] 

In the not too distance future, while fleets of commercial space ships travel between the planets of numerous solar systems, a traveler named Virgil Samms visits the planet Arisia. There he becomes the first wearer of the Lens, the almost-living symbol of the forces of law and order. As the first Lensman, Samms helps to form the Galactic Patrol, a battalion of Lensmen who are larger than life heroes. These solders are the best of the best, with incredible skills, stealth, and drive. They are dedicated and incorruptible fighters who are willing to die to protect the universe from the most horrific threat it has ever known. (Goodreads)