To encourage more participation, I think people should also feel free to post about books that they have recently read and enjoyed (or didn't enjoy).
People can also post about a theme they particularly like or something that bugs them they have discovered while reading several books. For example, on my own blog I posted a rant about how fat chicks are portrayed in chick lit, including in their own sub-genre of chick lit.
Please also feel free to post about favorite authors or your anticipation of a new book coming out by a favorite. Basically everything you want to talk about about books.