1991 Peter David
A feud between two families of space gypsies is about to end in marriage, as their children have decided to tie the knot and give Captain Picard the honor of marrying them. Although this species never been heard of before, and indeed never will be again, the ceremony is attracting guests from throughout the Federation, including...Lwaxana Troi. That certainly puts a damper on Picard's spirits, but then Q decides to invite himself to the festivities to explore the age-old question: what is love? Poor Picard. Poor, poor, Picard. If surviving a week of tense relations and petty bickering between future in-laws weren't bad enough, he has to do it in the company of the two people in the universe who drive him absolutely mental.
It's the setup for what is easily the funniest Star Trek novel I've ever read. Although the premise isn't stellar (aliens wanting to know about human love is rather tired), the execution was perfect. Lwaxana and Q are powerful, prickly characters -- a lot of potential, but they're easy to misuse. In David's hands, they're dynamite together, even when Q isn't sniping at Worf ("Oh, you'll all have to forgive Worf. He's just discovered opposable thumbs, and he's feeling overly confident.") and neither of them is giving the good captain fits. David also weaves in a couple of running gags and throws a very earnest and very naked young woman in Wesley Crusher's quarters. Even his mother can't help but laugh.
Were I in the mood for an adventure or some poignant comments about the human condition, Q-in-Law might not have been appropriate. But I wanted to relax, and it delivered magnificently. I've never enjoyed Peter David this much before: small wonder he was asked to write other Q books. If you like Star Trek TNG in the slightest, look for a used copy of this. It's nothing less than a riot.