[I was sent a copy of this book by the publisher, in exchange for an honest review.]
The Astounding Adventure of the Ancient Dragon caught my eyes because of its premise: an alternate retelling of Holmes's and Watson's adventures, in a "what if those two had been children at a boarding school, instead of adults in London?" As a long-time avid reader of Arthur Conan Doyle's stories, I couldn't pass up on that, although any potential reader has to be aware that these new adventures are, of course, not canon. (The original Holmes and Watson didn't meet before they were adults.)
This novel will likely provide an amusing and refreshing reads to middle-grade children: boys going on exploring an old school, hidden corridors, mysterious kidnappings, peppered with a dose of humour and "old chap" banter. Some quips made me chuckle more than once:
"I ask you to come up with a distraction and you decide to set the boat on fire? Is that best you could come up with?"
And were even reminiscent of a Princess Bride kind of humour:
“I must warn you, I am a fencing champion,” Holmes replied, taking a defensive posture.
“And I must warn you,” Royston said, yanking out another sword. “I have two swords."
Honestly, I laughed out loud at those ones.
I like boarding schools for a setting, and the latter had the makings for an interesting place, complete with a gang of local bullies and a head mistress who expresses her dislike for the heroes. Those are typical tropes, but I thought they worked well enough here, because they, too, were presented in a humorous way. The investigation and action are nicely balanced, the latter taking the main characters into fights that were easy to picture in my mind (though the former was a bit simple... but then, they're twelve). Sherlock was true enough to his original self to my liking: oblivious to girls, possessed of a lot of knowledge, able to notice small details (and with a bonus way of talking his way out of the teachers' wrath in an elegant and funny manner).
Last but not least, I found it easy enough to get into the concept of Holmes and Watson as children—which I wasn't sure would happen at first. As with every retelling or alternate setting, this is, in my opinion, a matter of either love or hate. A reader who wants to see Holmes act exactly as he does in Doyle's novels may not be completely satisfied; what worked for me here won't work for everyone.
I thought at times that the characters were able to do too many things (taking on opponents with a spear, firing a gun...): I can imagine how it fits an adventure-focused story, but the fact is, they're only twelve. Sometimes I also found them a little callous, dismissing the death of a goon as if it was nothing, or Watson not seeming to care that much about the sick mother her had left behind him. Again, adventure is a distraction for the mind... but they're still twelve.
I'm torn about the writing style. As an adult reader, I enjoyed it; the novel is well-written, and I could sense the same kind of vibes I'd get from the original stories, with the narrator (Watson) seeming to hit close enough a mark. It has a "gentlemen's banter" quality that is exquisite to me. However, I'm not sure a 12-year-old narrator, even a precocious one, would master language to such an extent. In other words: I liked it, but I'm torn about how to judge it in an unbiased way. One thing's for sure, though: the language wasn't dumbed down "just because it's for kids", and this in itself has to be commended.
You may also want to enact suspension of disbelief regarding the school itself: the action is set in 1865, and I highly doubt there were any mixed-sex schools in Great Britain at the time, lest boarding schools. If you're willing to overlook that in favour of focusing on the adventure, it'll probably be all right, otherwise it might keep nagging you.
(NB. I wasn't too keen on the illustrations, who weren't necessary in my opinion, and seemed to hesitate between looking like a child's drawing and "real" illustrations. This is a very minor quibble, though, which has nothing to do with the writing itself.)
I realise this review seems to contain a lot of criticism, and more flaws than merits. I've tried to write what I enjoyed, and what I found as being or not problems, in terms of intended audience especially. All in all, I enjoyed this novel, and think younger readers would also like it; but it definitely retains some aspects that could make it or break it for others.