I've been enjoying the community! Here are some thoughts I have!
Appearance wise - Would be cool to have a dark theme, even if it is the current theme turned dark. I like the blue - it's calming. I like the banner with the book included in it. The rest of the banner space appears to not be in use - I'm unsure if it is possible but would be cool to kind of have some kind of advertisement of discussions in that area, kind of like a "Featured Author, Featured Book, Featured something" Just one though because it would feel cluttered otherwise.
I like the organization of the forum. Simple - but it allows people to expand upon topics. I would create a topic in the Writing Tips and Feedback section talking about constructive criticism, because one it gives the empty forum a topic, and also it gives guidelines to people wanting/needing/giving feedback.
Earnable Badges for completing books and etc would be cool similar to Kindle in a way. Setting goals as a forum to read x amount of books as well.
Future recommendations: If the book discussion gets too full you could have subforums under it per genre. I don't think it needs that at this time yet though. I'm thinking more like 100 threads. I've read there may be interest in book clubs, I could see you setting up a forum under the reading area "Book Club" but there must be a book club application, there needs to at least be 3-4 people interested in participating in that book club before starting. I would do a book club per book, rather than a whole entire forum book club because people have different taste. However, that could be something you do as a community is try to read the same book in order to have discussions about the book. That could be a voting situation to pick the book.
These are my thoughts so far - but I'll continue to think about it. You're off to a great start and I truly do enjoy the community!