I apparently haven’t read any series that have novellas. I can only think of two that I’ve read, and did love, so that’s something.
The Tales of Beedle the Bard by J.K. Rowling
Debt of Bones by Terry Goodkind
I’m pretty sure most people know what The Tales of Beedle the Bard is about. The fairy tales of the Wizarding World. I really love it, and reread a story from it every so often.
Debt of Bones is a prequel novella for Terry Goodkind’s epic fantasy series The Sword of Truth. It takes place about fifty years before the first book of the series. It’s about one of the characters and a war that is happening at the time.