Now we want it to be a community，Would you like to share your reading experience and discuss it with others?
The discoverability argument suffers for two reasons. First, people don't read very interesting books. I've never came across something genuinely special that I hadn't already read, online. Second, books are already very discoverable - since universities prepare reading lists, authors recommend stuff, and books reference each other.
The first problem holds for whatever you consider an interesting book - unless, perhaps, you like bestsellers. Reading is by nature a very fragmented passtime - and no two readers have the same taste.
The possible exception to the first problem is in itself a problem - popular books tend to drown out the less popular ones - until your book forum no longer helps discovery since it just talks about very discoverable bestsellers.
I'd only really be interested in a book forum if it offered something very different to what exists already. I think it would be interesting, for instance, to have a domain-specific set of forums (say, 'victorian gothic', 'medieval european'), then have a hard test that you have to pass to post in them. I don't think this would work either - but it would be different.