The book isn't known for being particularly funny (other than some of its more laughable plot elements and the Narm which crops up, but this was probablyunintentional), but some moments do stand out:
After Han's rather questionable decision to use the Gun of Command on Leia and kidnap her off to Dathomir for the titular courtship, he stows her paralyzed body in the smuggling hold. When the ray wears off and she starts banging on the panels to be let out, who should find her but Threepio...which leads to this exchange.
Threepio: Mistress Leia! Whatever are you doing down there?
Leia: I've come to kill Han, and this was the only way I could get on board.
Luke faces a Dathomir witch who is using telekinetic attacks similar to Darth Vader's to bombard him with debris. Shortly before getting slugged in the head by a heavy object, Luke dryly notes that Vader wasn't this good at such attacks.
Han is tortured by a Dark Side witch, who, amongst other injuries inflicted on Han, uses the Force to shatter one of his teeth. Which wouldn't be funny at all, except for the Smooch of Victory Leia smacks on Han after they rescue him a few scenes later, leading to a most undignified (and muffled) scream of pain.