A neatish novella by a talented author that is lessened by the work that it critiques. The idea of the novel is similar to Atwood's Penelope, except that rather than critiquing and re-imagining the role of women in the Odyssey, this book critiques and re-imagines the role of women in comic books. So you have a Spiderman chapter written by a Mary Jane type character, a chapter by a Queen of Atlantis, a chapter by a Harley Quinn stand in, etc. etc. The basic problem with this is that everyone already knows that the earlier comic books were all terrible. They were intentionally terrible. The comics were written for teenagers, and not high quality teenagers either. So this is a bit like writing a book critiquing the marketing copy on your cereal box, or complaining about the NYTimes Editorial section. It's like "yes, they are bad, they are intentionally bad, and if you are taking them seriously you are giving them more credibility than they deserve." There is also the issue that this critique is super-common these days, e.g. in the last year there have been not one but two Harley Quinn treatments that make many of the same points that this book does.
This is a shame, since the author herself is quite good. She is clearly a comics super-fan, and her ersatz versions of the well known characters and story lines are consistently creative, grounded, and fun. She's a skilled world builder and story teller. I would *much* rather read a straight up super-hero story written by Valente, than read her critique of terrible comics from 30 years ago. And now checking her wikipedia page... she is super prolific and I actually have read another one of her books before. So there you go.