I like to think of it as my "Zombie Robot Unicorn" meter. Basically I liken my current reading habits to an internal image of a Zombie Robot Unicorn and use it to describe my current thoughts about whatever I'm reading.
In practice the image shifts to a much more "zombie-fied" robot unicorn in October and perhaps a bit more "Unicorn-ed" Zombie Robot during the winter.
Over the weekend however I went through my book award and top 100 lists I've been reading my way through over the last decade and realized that I'm actually steadily reading more Science Fiction than either of the other two and have been for some time...
I guess my Zombie Unicorn is much more robotic that I've previously though.