Endymion Spring is an exciting children's book, that gives a nice (if basic) introduction into the world of the humanities and how they work. It speaks of libraries and the Middle Ages and the coming up of the printing press. The read was interesting, I found myself turning page upon page. There were little things that bothered me (most particularly Duck, who really grated on me) but overall it was an enjoyable experience.
Then I came to the historical notes. I had been wondering about a few little things with respect to historical accuracy in the book before. What fascinated me was that Matthew Skelton named both Laurens Coster and Johann Gutenberg as inventors of the printing press. This is fascinating, because Laurens Johanszoon Coster, a Dutch guy from Haarlem, is/was (depends on who you ask, there's still a memorial for him in Haarlem) in the Netherlands believed to be the inventor of the printing press. Germany generally believes it's Gutenberg, and Gutenberg has got the most support in the world (and is honoured, for instance, at the Project Gutenberg). Matthew Skelton however says in his notes that he believes he has found "a long-forgotten secret": Laurens Johanszoon Coster is the inventor of the printing press, and that the world is making a mistake.
Because we've just discussed this in class, there are a few things I wish to say. My Professor knows pretty much everything there is to know regarding the (German) Medieval time period. She is absolutely convinced that, if you want to name a particular guy the inventor of the printing press, it should be Gutenberg. (Though based on the evidence, it is only fair to say that in Asia people had experimented with printing long before it happened in Europe.) Supporting Gutenberg's claim has for her, my German professor, nothing to do with patriotism. There is quite a lot of of proof for this, her statement is backed up by various experts and historians. Better said, (nearly) everyone who has knowledge of the subject says the inventor must have been Gutenberg. As far as I've heard, there are even people who are still debating whether the story of Laurens Johanszoon Coster "inventing" the printing press is a myth or not: a problem Gutenberg doesn't have, because there's a lot of evidence to be found to name Gutenberg as the inventor.
Basically speaking, this conclusion in the historical notes rubbed me the wrong way. If you want to open up the discussion, don't do it based on three books and claim to know the truth from those, if pretty much everyone else who has knowledge of this topic, disagrees with you. Based on this oh so vital thing, I have trouble believing the rest of Skelton's "research". *
(Also, your leaf dragons are a nice idea, but instead of being inspired by a relatively modern author (Jorge Luis Borges) you could, of course, have opened an actual medieval bestiary, I can assure you they are interesting and would have given you plenty of material to work with. Not that this particularly bothers me, but it might have helped with the extra medieval vibe to your story.)
Thankfully the story was mostly enjoyable, so I can mostly set aside my issues with the research. But I can only say this: if you do know something of the time period, there are many little things that may fall flat for you. If you aren't familiar with the time period, then this is an exciting ride of two kids, a magical book and medieval influences, which you may very well end up liking.
* I may not even have read 3 books on this subject, but my Professor has and so did the experts in the documentary I've seen, accepting Laurens Johanszoon Coster as the inventor of the printing press really does seem dubious at best. Possibly it would have been better if Matthew Skelton had used the discussion and Dutch myth as inspiration, instead of so publicly choosing sides.