Absolutely boring
Well, first I'll introduce myself, I am spanish and I've seen the movie the day of the releasing (really dissapointed me, feeling so stupid after spent 6 euros on 2+ hour of boredom) and I've read 4 of the books of Alatriste by Arturo Pérez Reverte, one of my favourite writers (check his latest book, "El pintor de batallas", it's really good). So expect faults in my english, excuse me.
You have to be very careful when making a movie from a book (or 5), because although both cinema and literature both explain stories, they use very different ways to explain them. I've seen other movies that do the same mistake, instead of considering the power of the story given by the books and do some adjustments, they use the book as script for the movie.
And when you have 5 books, the movie becomes a mixing of unconnected scenes with too much action in them, that doesn't let the spectator to live with the characters what's going on in the screen. You ask yourself too much times (What the hell is happening now?).
It's a fast movie, it does happen a lot of things, but at the same time it's slow, because it's boring (you will wish the movie to end, and it will seem to you it never does) . It feels like a 5 hours movie being cutted to be "only" about 2 hours.
Viggo Mortensen acts very well, although his spanish is, let me put the definition of my sister when she heard his voice for the first time, "He has voice of a mental retarded person". I never heard the voice of Viggo when acting in English, but I suppose it's better than the spanish one. I suppose if you don't see the movie in original version that won't be a problem, but in the cinema his first words make the people in the cinema laugh and make some comments. Later as you are more familiar to his voice, it doesn't become a big problem, but I think the movie will improve if someone had dubbed him.
Actors are good all, great Javier Cámara, Ariadna Gil, Elena Anaya, Juan Echanove, Unax Ugalde (the best in my opinion), Blanca Portillo (although it doesnt seem a man, maybe I've seen her too much times in TV), Eduardo Noriega too. The problem isn't there, as it isn't in all the work to bring to life all the 17th century Spain, the movie is well done here.
The problem is in the script, bad adaptation of the books, bad in the pre-production. Bad in puzzling all the scenes that has been filmed, or that had to be filmed in some other ways, to use the power the cinema has.
Final result is boring, endless, confusing, and ridicolous at the end of the movie. When the final titles displayed I felt like being stupid of being there.