This book is basically a fairy story. But not the nice safe Disneyfied kind where everyone lives happily ever after and no one really gets hurt. No, this is the older, darker kind of fairy story, the kind where you need courage, virtue, quick wits and a healthy dose of luck to survive - and even that may not be enough.
As World War II begins, David is desolate after the death of his mother. Things aren't helped by his father's rapid remarriage and the birth of his new half-brother. David seeks escape through books, but one day that escape becomes entirely too literal and David finds himself in a strange new world where stories have a life of their own. This is for the most part, a nicely written book, in a style that's just reminiscent of "Once Upon A Time" stories without overdoing it, and David is a good protagonist - not a perfect paragon of a child, flawed and uncertain but doing his best anyway.
The author apparently spends a fair bit of time in the USA, which is unfortunately apparent from some of the inappropriate Americanisms that crop up in this book. There are a few minor things, like saying "closet" and "drapes" where an English person would say "cupboard" and "curtains", which I've got used to in fan fiction in British settings from American writers, but hadn't expected to see from a published author. Worse than that, he describes David as feeling as if his hand and cheek had been brushed with poison ivy, which does not grow in England and never has. That's the sort of thing that the author should have checked, and failing that should have been picked up by an editor.
The other thing that irked me about the book is that it's 502 pages long, but only 348 pages of that is the actual novel - the rest is author's notes, describing the tales he's referred to in the text. Now, I don't object, on principle, to author's notes - they can be interesting and informative. But when the author's notes are nearly half as long as the book they refer to, it suggests to me that either the author doesn't think he's got his point across properly in the book itself, or he's entirely too pleased with his own cleverness and needs to get over himself.
Still, a good book, and worth reading.
 Even modern day British people rarely use the word, but in the 1930s and 40s it would have been even rarer - except for water closets, but those are a rather different thing :-)