Ill Seen in Tyre by Steven Saylor
Young Gordianus and his tutor Antipater have arrived in the latter hometown of Tyre on their way to the Hanging Gardens of Babylon, but Gordianus finds out that his mentor has a soft spot for illogical magic and mythic heroes. While staying at a tavern, Gordianus learns of the local heroes Fafhrd and Grey Mouser who had very roguish adventures in the city and interacted with Antipater's grandfather on one occasion. But all of this is prelude to Antipater purchasing the Books of Secret Wisdom and both of them getting taken in by the seller and possibly everyone in the entire tavern as well. But Antipater doesn't care and Gordianus, while furious, has to let it go. The story itself gets a tad predictable when the seller arrives, but the highlight was the descriptions of Fafhrd and Grey Mouser which were created by Fritz Leiber and who I know what to read myself.