I like the idea of themes; my own suggestion would be "Books with a word related to time in the title." It would be fun to shake things up from strictly genre-based nominations and it would have the benefits of both avoiding a wrangle* about whether or not a book fits the genre and allowing more broad-based nominations.
I'm ready myself to move forward on expecting that those who vote will participate in a discussion. The current "vanity contest" (great phrase) isn't conducive to a vibrant club. There's value in discovery, yes, and nominations benefit from broad input, but once we move past that phase the voting should reflect those who will actually participate in the second phase. Lurkers, which I totally understand, also will benefit from an active discussion and droppers-in are entirely delightful as well, too. The book club wouldn't cease to be welcoming or open to all comers, but people could decide in any particular month if they were going to participate as lurkers, nominators in the first phase, droppers-in in the second phase, or totalitarians.
*I'm also ready to see an end to the wrangling; that's in fact the top of my wishlist. No criticisms of other nominations and while electioneering is fine and fun, it should consist of positive comments about a particular book rather than negative comments about others. A good-humored tone should allow people to get their point across!