Lord Valentine's Castle is a novel by Robert Silverberg published in 1980.
Review of "Lord Valentine's Castle (Lord Valentine, #1)" on 'Goodreads'
4 stars
One of the few books I read as a child and enjoyed every bit as much as an adult. That's been a rarity for sure.
Silverberg delights with his wildly imagined world, his involved (even if occasionally tedious) politics, and his fun cast of characters.