They don't hang out on the internet, they are reading books :D
More serious answer: Goodreads.
I am making a small website that would be useful for book readers. Where can I promote my product?
Second Goodreads... Kindle integration is a big plus!
Still Goodreads, but damn, that site is ugly. But this is where my community is hanging, so...
(From my personal experience) I've visited:
Nowdays Facebook Groups took over (mostly due to their convenience and ease of use).
Goodreads, Amazon, and Audible are the only book related sites I visit.
Producr Hunt is a good place to show/promote book related websites! I had mediocre succes with wits.io where i got almost 100 paid signups via product hunt. I am also working on a telegram community but havent posted it on ProductHunt yet, wits.chat
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