Brevity in descriptions would, I think, accurately describe how Leiber dispenses his prose in the service of settings and locales. This is reflected in the bulk of his oeuvre consisting of short stories, novelettes, and the like. His novels are few. Sure, he is the master of complex, lengthy sentences, of which he likes to start off his tales, and likewise he sometimes employs lengthy paragraphs when setting up the stories. What you won't see is pages upon pages in the service of description. Instead, all that needs to be communicated is put forth in that lengthy sentence or paragraph with brief mentions of sundry activities, inhabitants, and items, leaving the reader's imagination to paint in the details. Leiber entices the reader to tell part of the story too, which is appropriate given his settings of murkiness and mystery. Leiber paints the scenes in broad brush-strokes, inviting the participant to dab in the details with their fine-tipped brushes.
If you are a Gamemaster running an RPG in the environs of Nehwon, this is a boon for your purposes. Leiber has created a skeleton of a world for you and your players to flesh out. Yes, these bones may already appear to be clothed with plenty of flesh upon them, but similar to Nehwonian Ghouls and their transparent flesh, what appears at first fools the eyes. If you examine closer, there is much left for you to stitch together.
The Cloud of HateThe Mouser said dryly, “I already smell dead fish, burnt fat, horse dung, tickly lint, Lankhmar sausage gone stale, cheap temple incense burnt by the ten-pound cake, rancid oil, moldy grain, slaves' barracks, embalmers' tanks crowded to the black brim, and the stink of a cathedral full of unwashed carters and trulls celebrating orgiastic rites–and now you tell me of a taint!”
The Two Best Thieves in LankhmarThe hawkers of drugs and strong drinks forbidden by day had not yet taken up their bell-tinklings and thin, enticing cries. The pleasure girls had not lit their red lanterns and sauntered insolently forth. Bravos, desperadoes, procurers, rubbed drowsy sleep from eyes yet thick-lidded. In fact, most of the Night People were still at breakfast, while most of the Day People were at supper. Which made for an emptiness and hush in the streets, suitable to Night's slippered tread. And which created a large bare stretch of dark thick, unpierced wall at the intersection of Silver Street with the Street of the Gods, a crossing-point where there habitually forgathered the junior executives and star operatives of the Thieves Guild; also meeting there were the few free-lance thieves bold and resourceful enough to defy the Guild and the few thieves of aristocratic birth, sometimes most brilliant amateurs, whom the Guild tolerated and even toadied to, on account of their noble ancestry, which dignified a very old but most disreputable profession.