The Second Book Of Lankhmar by Fritz Leiber
After their legendary adventures in the northern wastes and beyond, Fafhrd, the giant barbarian warrior, and the Gray Mouser, master thief, novice wizard and expert swordsman, are back home in Lankhmar again, and looking for an easy time.
But Lankhmar is under attack from a strange horde of invaders, including a two-headed dragon and an army of miniature wanderers ... Once those threats are seen off, a quest to the farthest reaches of Nehwon is in prospect. And then, in the last book of their adventures, Fafhrd goes sailing through the clouds, and the Mouser takes to the seas, before we finally bid a fond, if sad, farewell to Lankhmar.
THE SECOND BOOK OF LANKHMAR includes the last three volumes of the hugely enjoyable series.