Intergalactic P.S. 3

This book is presented as a standalone story from the world of A Wrinkle in Time. But in reality, looking at the publication date, it just seems to be an early draft of a portion of A Wind in the Door. So if you've read Wind, you don't need to read this book. That being said, I do think the story depicted is one of the most interesting parts of Wind, so I think if you can set aside expectations that it's an original story, it's an OK book for kids. However, I'm not really sure who the audience for this book is. It's written in a lower reading level than Wrinkle or Wind, so it seems like it's maybe for a younger audience who aren't ready for the other books. But I'm not sure it makes enough sense on it's own if you don't know the characters already from Wrinkle.