I've read Kaiju Preservation Society. It's very entertaining and I'd highly recommend it. I have The Spare Man on my to read list because I liked The Lady Astronaut series by Mary Robinette Kowal. But from the description it sounds more like a murder mystery - IN SPACEEEEEEEEE - than a real sci fi book. The other nominees aren't traditional science fiction books, either, they're more fantasy or fantasy/horror.