The story of a girl with two moms who is about to get a sibling, this is very much a story about their family’s own experience, told from the perspective of the older daughter, with photos of their family as the illustrations. One mom is pregnant, and the book takes us from her pregnancy to the birth of the child and their initial time as a family of four. There is no discussion of how she got pregnant; the focus is on the feelings around growing the family, not the mechanics.
It may not fit all families—families adopting a second child, multiracial families, or families with a son, for example—but I think some of the first child’s feelings may be similar. And that’s less a criticism of this specific book than a reason we need more books featuring LGBTQ families of all types.