Every Heart a Doorway is the first book in the Wayward Children series, and the last of the novellas nominated for a Nebula that I'll be reading this year.
McGuire is a very competent and prolific author. I am familiar with her through her Newsflesh trilogy (here is one of my reviews) which was aimed more at adults, but a lot of her work is aimed at teen girls. Every Heart a Doorway is one of those.
The story is fairly basic. Our protagonist is one of a number of girls thought to be kidnapped, but actually having visited an alternate reality through one of many fairy-tale type doorways that open up to those who look for them. There are a few boys, but mostly it is a girl thing. The girls sometimes return from these alternate realities, willingly or unwillingly, and are thus reunited with their families, but are permanently changed by their experiences. They don't fit here anymore, and the ones sent to Eleanor Wilson's Home for Wayward Children want to go back to their alternate worlds. The actual plot in this book is a murder mystery--the girls are getting killed one by one--but mostly it illustrates the alternate worlds. It's all pretty orderly--there are major and minor axes for the types of worlds. There are a few plot inconsistencies that cause grief in this orderly universe--the worlds the girls discover "fit them well" and they want to go back, but there's also a mention of another home for those who hated their alternate world experience and don't want to go back. Oops.
So this is another fairly well executed, not overly original book by McGuire. If you like the rest of her stuff you will like this. 3 stars.