Smashwords isn’t Nostr; it’s an online distributor. 

There’s Creatr which is like the Nostr version of Patreon. I’m looking into that next year to publish my fantasy novel. 

There’s long form Nostr clients like Yakihonne and any Nostr account can set up an npub.pro website which can be a way to consolidate an ongoing written work. 

That’s what I know of. Interested to see what other answers you get .