Yes! Leanpub has mostly been popular with authors of technical books because in-progress publishing, and books that can be instantly updated, are powerful tools for people writing about cutting-edge and constantly evolving subjects.
We would love to see more fiction on Leanpub! We think a good model for self-published fiction authors is to write and publish in-progress on Leanpub, and then when you're done, you can and should try distributing your book through other book distribution channels, including Amazon.
Here's our pitch to romance authors: https://leanpub.com/romance.