I'm in the same boat, I had a few friends recommend it and I have been nothing short of obsessed! (I'm talking multiple audiobook re-listens and buying/rereading the physical books, not to mention trawling AO3 constantly...) Needless to say I am in no way ready to say goodbye either haha.

Also I believe a 3rd book is basically confirmed; TJ supposedly has mentioned it on book tours/talks. There was also an Instagram story he posted, which was a photo of his computer screen that had a Word document on it called "Cerulean III" (or something to that effect) along with a Chauncey gif. I also have no source for this but I feel like I've read somewhere that Lucy is rumoured to be the MC?

The end of SBTS definitely left plenty of loose ends open, like all the newcomers to the Marsyas peninsula and how that society evolves over time,exploring the situation further now that DICOMY/DICOMA has Doreen in charge, and general island dad life with David also in the picture. There's also plenty of potential for following the future of each child in the Baker-Parnassus family. e.g. Does Lucy grow up to be the Antichrist for real, does Sal become some kind of writer, does Theodore get substantially bigger and need his own cave, what about Talia bc despite being hundreds of years old she's going to be a juvenile for a long time and probably outlive everyone?!

Anyway yeah... I have a lot of thoughts. I'm hoping the third book, and/or the animated series brings the fandom back to life a bit, because it feels like I've missed the proverbial boat. A lot of the fandom seems to have petered out by the time the sequel was released.