I thought the first book was a bit fantasy-autobiography with the nerdy heroine a stand-in for the author. That was probably silly (and maybe a bit condescending) of me. The characters in this are quite different, and I doubt that both heroines (or some combination of protagonists from both books) can be autobiographical.
Kingfisher's writing oozes cleverness, but in a fairly undemanding way. The romance tropes occasionally verge on the self parody, but I can't swear that isn't intentional.
As a fantasy (in the non-romantic sense), the world building and characterization are rather good.