Madouc is the third book of the Lyonesse trilogy, and it does a fantastic job of wrapping up a lot of the storylines/ends from Suldrun's Garden and The Green Pearl.
Vance tells his story with such a dry delivery, that at first, you might not catch the humor if you aren't looking for it, or, if you don't like that kind of sardonic telling, you might just not enjoy it.
This whole book is so silly, so hilarious, fast and fun... but you aren't being told that it's hilarious and silly, which makes me love Vance all the more.
It's like he thinks his readers are intelligent enough to figure it out without telling them what to do, which I very much appreciate.
Princess Madouc, who doesn't know she is a changeling, is suffering from a crappy childhood in the same style as her "mother" Suldrun. Only she's not the passive Suldrun, but a very spunky and awesome Madouc, and so, shenanigans ensue.
And there's a satisfying happy ending... sometimes I just love those.