I was actually surprised I found out about it as late as I did. I've been a huge fan of the book series for a couple of years now, but since I live in North America it is titled The Last Apprentice. I figured that it would get that name instead of the Spook's Apprentice or even the Wardstone Chronicles. I was completely surprised when Seventh Son was chosen, but I figure that it has just that much more mystique to it than another chronicles. The funny thing is, that when I read books, I imagine the characters in my head. I created original people for all the characters but John Gregory, after watching True Grit, only Jeff Bridges fit that role. I was happy when he was cast.
So, I haven't read the most recent novel on Grimalkin, but from my analysis of the trailer, even though Ben Barnes is a decade too old, the film looks pretty good. Now, I'm not one who complains about staying true to source material, because I personally believe that a film should deviate, because I believe in a multiverse. I believe in getting different adaptations of the same story. Hence, I believed that a strict adaptation of the first film, too off, especially since I think that the first novel is too short and not action packed to have a successful film adaptation. So I was glad at how they deviated, the effect it added was unique. Nonetheless, I still believe a younger actor would have done fine, but if Emma Stone and Andrew Garfield can play teenagers, so can Ben Barnes. But, now, don't trust wikipedia, it says 14, don't trust it. They probably amped it up so that he's nineteen and this is the late seventeen hundreds, not early 1700s or late sixteen hundreds. One thing I don't trust, however, Sergei Bodrov, after Green Lantern, the only older directors I trust are the ones that are more well known (Campbell was just a James Bond fluke to me).
My analysis of the trailer is that it will be a loose adaptation of the original novel. It introduces some new characters and so forth, but the basic plot appears to be the same. Coward Tom Ward is chosen to be the new Spook, Malkin escapes, Ward trains and ends the Malkin threat. Same story as the novel, it is what happens in between that I want to know more about. I saw some Hindu demon (or was it God?) in there, weird ogres and trolls and the power of the witches. It appears that they took the original book, drained it dry and put it on Bane's Venom. Honestly, though, say the film has four acts, it appears it will have at least two action scenes, one at the beginning and one at the end. From the look of things, it seems very good, but could very well turn out to be Eragorn 2. We saw hints of character development and action all around, but don't go right away. Wait for some reviews to come out, but don't worry, it comes out next year.