I have no idea why this children's book trilogy is so hard to find. At its heart, it is a fairy tale (I seem to read a lot of those come to think of it) about chivalry, honor, and hope. Helprin writes in his typical fanciful style, which is somehow opinionated, dense, and fun at the same time, with countless parallels to Winter's Tale. Illustrations are by the same artist who drew Jumanji and The Polar Express.
The three books collected in A Kingdom Far and Clear are different in tone and narrative viewpoint but also tell a single story effectively, with more ups and downs than the typical fairy tale. The second one is my favorite because of a moment when science and faith come together absurdly and beautifully like the sun and the moon in an eclipse. Let's just say it has to do with a blatant violation of the laws of thermodynamics, and the fact that I'm even mentioning this about a children's book shows you what a brilliant book it is. All I know is, because nobody seems to know about this book, I have a ready-made gift for children whose parents will read to them, because this book is an incredible find.