Amazon stats as of this writing:

#1 in 	 Kindle Store > Kindle Books > Science Fiction
#5 in 	 Kindle Store > Kindle Books > Fiction > Genre Fiction
#8 in 	 Kindle Store > Kindle Books > Fiction > Contemporary Fiction

I think John Scalzi has arrived, as the parlance goes.

Kindle-licious review
Buy Zoe’s Tale in Kindle Store