For Kim Stanley Robinson, my favorite of his works is the Mars Trilogy. Like all of his work it can be a long slog, heavy worldbuilding, pages and pages of geology, etc. But all of it’s good, like an epic story wrapped up in a fascinating nature documentary, all imagining a better future.

Another one I'd add, that’s very sci-fi and also very solarpunk, is Jayan F.R.’s novel The Wind of Venus (set in a community of airships floating around Venus). It’s a wholesome coming of age story for the first half, then there’s more action the second half. I gather it’s book one of a forthcoming series.

I also strongly second Ruthanna Emrys’ A Half Built Garden, hopeful sci-fi first-contact story, and very solarpunk. Susan Kaye Quinn’s Nothing is Promised series is a great read too, more near-future climate tech intrigue on Earth.

The Steerswoman series by Rosemary Kirstein. Some of the best pacing I've seen in world building. The way the setting unfolds is incredible.

It's not solarpunk but does have interesting social structures that can fill some of the same needs.

@Star12Mt

For optimistic sci-fi, I like Kim Stanley Robinson. He could start with NY 2140.(Some of the others, like The Ministry for the Future, start out grim or have ups and downs, but are pretty optimistic in the end.)

I would imagine the same goes for The Martian (same author), although I haven't yet read that book. The movie was great though.

@Star12Mt Your husband might like my solarpunk power grid mystery novel series!
https://susankayequinn.com/series/nothing-is-promised

But I've also got a couple solarpunk short story collections and a podcast BRIGHT GREEN FUTURES with even more suggestions:

https://brightgreenfutures.substack.com/

https://ohai.social/@bluejay/116199280203005571

Also, A Half-Built Garden by Ruthanna Emrys is also great! https://app.thestorygraph.com/books/eec66b70-50ce-4341-880c-117f026e7390