Dragon Rider (Drachenreiter) was my favourite book as a child, so take this with a grain of salt.
This movie adaption has two issues: A) it is a very bad adaption, and B) it is also not a good movie.
The book is a fairly simple fantasy adventure with a touch of drama.
The movie, however, still managed to dumb down every aspect.
The biggest mistake was the change of genre into a comedy. Everything in this movie is supposed to be "funny". The original book is a lot of things, but funny is generally not one of them, so the source material was a wrong pick to begin with.
In the book, the dragons were mythical, the journey is long and difficult, and the enemy an ever-looming, terrifying threat.
In the movie, the dragons are goofy, the journey is an irrelevant side issue, the enemy is goofy. And the genie is a magic TV.
At the beginning of the movie, we are told a background summary of the world we're in, and get a look into the mundane everyday life in the dragon valley, both new additions.
Unfortunately, that takes a lot of the original mystery and feeling of uncertainty out of it. In my opinion, it just steals time from the rest of the story.
From beginning to end, the movie is overly vocal about HUMANS BAD. If that was picked as the most relevant point, then show, don't tell.
Most of the characters become lame stereotypes with little development. Firedrake ("Lung" in German) becomes a fool. Sorrel (Schwefelfell - "Sulfurfur") is reduced to a mean kid nobody takes seriously. Ben becomes a lying fraud. None of them retains any particularly likeable or interesting traits!
My biggest gripe is with how stupid and careless everybody is.
The calculated, but necessary risks from the book become a whimsical "oh yeah sure why not" in the movie.
Nothing seems deliberate, no decision is dangerous. Nothing happens for any specific reason. Every event is out of place and just kind of randomly pops up (suddenly, dwarves. Suddenly, desert. Suddenly, the villain and the genie have a battle. Suddenly, Ben finds the rim of heaven "because magic".)
It was just a mistake to squeeze a months long journey into a one and a half hour movie.
In the movie, crucial events work out just because the dragon and the rider are special and magic. In the book, neither of them was any special, which was kind of the point.
All in all, it is a rather unintelligent film.
The movie opted to leave out most things which made the story unique in the first place, and which filled me with a sense of wonder as a child:
The central alchemistic themes, the Himalayan monks, the relevance of the moon.
But most importantly, the real secret of the dragonfire, which Firedrake had no issue breathing in the book, and which could not harm normal living beings.
As a result of that, the end of the villain is actually much more brutal in the movie than in the book - he is literally burned and melted to death, all of him, on screen, by the heroes, in a children's movie.
Technically, the renders sit somewhere at the edge of the Uncanny Valley for me. It's not bad, but also not comfortable. Speed of movements is off. Pacing is off in many places.
The music is neat, but mediocre.
My two positive points: very fitting, good voice actors and some nice scenery.
There are some child-friendly movies that are witty, funny, intelligent, and/or tell something of value, but this is not one of them. Park your children in front of Upside Down, How To Train Your Dragon, Zootopia, or get them a copy of the book Dragon Rider.
