This is one from the first set of covers Gaughan did for Pyramid paperbacks of the "Lensman" series; some later printings used the same art but it was clipped or shrunk - with white borders. While I also like his "psychedelic" set, I feel that this set best captures the classic "space opera"/epic sweep of the series.

Kimball Kinnison was an Unattached Lensman, popularly called a "Gray Lensman" for the color of his leather uniform. This was the highest honor the Patrol could give. It meant he answered to no one, was under no supervision; any expense or project he comes up with is automatically authorized. But with this freedom came crushing responsibility - he was expected to best determine how to defeat Boskone from attaining its goal of smashing civilization! During the battle to destroy the pirate's Grand Base commanded by Helmuth, Kinnison had some suspicions about Boskone confirmed. The first was that Helmuth was not the top, and the second was that Boskone was getting support from (and possibly originated in) another Galaxy. To test his theory he plans an expedition to this other galaxy, and the Patrol gives him their best ship, the Dauntless, along with some of their best personnel including 10 Lensmen, to make sure he does come back. When they arrive, they find most of the galaxy under Boskone control, but encounter one planet, Medon, which escapes with a little help from the Dauntless. The Medonians had mounted super-Bergenholms, and the whole planet was "free" - able to cruise at super-light speeds.

On his return, Kinnison sets in motion some projects to develop super-weapons capable of defeating well-guarded planet-sized bases. Realizing that Boskonians run things from a "top-down" organizing principle, and that Boskone had many tentacles or branches, Kinnison decides to work his way up the ladder of the drug-suppliers, using a variety of disguises and identities, always seeking the top link, and who he reports to. The most memorable of his disguises is "Wild Bill Williams, meteor miner" - while apparently senseless after a drink-and-drug binge, he is reading the minds of the zwilnicks he tracks. At the same time, the Council of Boskone are forming their own theories about this lensman, "Star A Star" (as they call him), who is responsible for their recent series of setbacks and defeats. Kinnison and Worsel (who is also a Gray Lensman by now) use the information gathered to mount a mission to spy on the Council of Boskone, the Eich themselves. The Council buys his subterfuge of being a lesser pawn of Star A Star, and after breaking him, return him barely alive as an example to discourage his leader. At great cost, Kinnison has obtained the information the Patrol needed, and those planet-busters he had them develop earlier are put to good use. [This was serialized in 4 parts in Astounding, beginning October 1939.]