I was particularly interested in this book for its historical perspective of the rubella epidemic in the 1960s and resultant disability from the vantage point of a family's experience. As it ended up, that seemed to be more of a subplot to the book, which, on reflection, is exactly what that experience would be for the tween/teen narrator. There's a lot going on in a young girl's life at that time, and not every moment of it is going to involve thoughts of her baby sister. In some ways, that's actually it's own message--this baby is just a part of the family and sometimes that's incredibly hard and sometimes it's just incredibly normal, because that's what life is like when there's a child with a serious disability or chronic illness in a family.
Further, it was nice to see a representation of historical fiction for middle grade readers at a time when a lot of middle grade seems to be gearing toward fantasy. I recall when I was in grade school gravitating toward books like Betsy Tacy, Anne of Green Gables, The Secret Garden, Little House on the Prairie. This genre doesn't seem to be quite as robust as it once was, and I loved it so much when I was younger.
The writing here is also quite good, leaning into some more mature topics such as the pejorative descriptions of people with disabilities and the (accurately portrayed) views of the medical establishment toward disability in 1960s. So the book sits at a place where it can challenge a precocious young reader who wants/needs stories with more complexity.
I will offer the disclaimer that the book is also genred as Christian fiction which is a genre I have never read before--I had to google it to know what the tropes and structure of the genre usually are. Even with that, I did not find the religious elements to be heavy handed. Moreover, I thought Debbie (the protagonist) interacted with religion and spirituality in a pretty typical twelve-year old way, with wishful praying and bargaining that simply rang true to me.
All in all, I would recommend this book to sophisticated young readers who gravitate toward realistic/historical fiction at a time when so many of the books available to them aren't that.