First Lensman. by E. E. Smith

Against the backdrop of a secret war between two all-powerful alien races, Virgil Samms of the Triplanetary Service is selected by the seemingly omniscient Arisians to be the first bearer of the Lens. Only individuals deemed brave, virtuous, capable, and incorruptible can receive a Lens, which grants its user telepathy and other powers. With it, Samms seeks out other "Lens worthy" humans and aliens, with the goal of creating a Galactic Patrol that will defend planets adhering to Civilization from corruption, vice, and piracy.
First Lensman is the second book in E. E. Smith's Lensman series but was the last to be written. Unlike the rest of the series, it was never serialized, and was first published in 1950 to help link Triplanetary with Galactic Patrol. Smith's imaginative and bizarre alien races are on full display, as well as the constantly escalating space warfare that is the hallmark of the space opera genre.