I'm working on a much longer, more in-depth and slightly spoilery (if you've read the books) review for later on, but here's a much briefer summary of my thoughts to be going on with from last night's screening of the first two episodes of Game of Thrones.
As with the book, this is a big, complex story with multiple plot-lines and a significant number of characters with their own motivations and story arcs that need to be established. Even trickier, there is a significant amount of backstory to set up, along with discussions of characters who have been dead for seventeen years when the action starts (they may turn up in flashback later, but they certainly don't at this point). With the action unfolding in multiple locations on two continents, the potential is there for the whole thing to collapse under its weight into a huge mess.
Thankfully, it doesn't. The script and the acting does a good job of introducing us to the characters briskly and efficiently, but hinting at depth and more complex motivations. The main cast give uniformly great performances: my more in-depth review will cover this, but Peter Dinklage, Maisie Williams, Mark Addy and Harry Lloyd are outstanding, and Sean Bean's performance has an element of humour and nuance to it that I think will surprise some, whilst Richard Madden does great work with only a limited amount of material. Dialogue - much of it taken directly from the book - is mostly strong, but there are a few clunky moments during sequences of exposition. Particularly notable is the presence of humour: the audience I was with laughed quiet a lot at Arya's antics and some of Tyrion's lines.
The script is faithful to the book, though a couple of fan-favourite scenes are exorcised for time reasons and some new ones are dropped in to help clarify certain characters and storylines. The success of this is mixed: the establishment of Robb and Sansa's characters are hurt a little by the removal of some scenes, but Cersei and Cat's are helped by the insertion of new ones.
Problems emerge in Pentos and the Dothraki Sea scenes. Daenerys doesn't have a huge amount to do at this stage and Emilia Clarke does good work with what she has, but her character isn't strongly-established at this stage. Jason Momoa has little to do other than look buff and show off his arse a lot, both of which he handles well. Whilst events in Westeros are mostly free of cheese, a distinct odour of Stilton emerges in scenes involving the Dothraki and Dany being taught how pleasure her man by a bed slave (though British fans may be distracted at this stage by, "Hey, it's that girl off Hollyoaks,"). These scenes are uplifted by the presence of Harry Lloyd as Viserys, who is outstanding and actually makes the character work better than in the novels, and Iain Glen as Ser Jorah Mormont, who makes scenes 150% classier just by showing up. Still, the Dothraki sequences skirt around the edges of corn and could be problematic for some viewers.
Overall, we have a show that isn't 100% brilliant out of the gate, but one that lays out some very strong foundations to build on. The problems are ones that to some extent were unavoidable, and none are terminal. The cast is fantastic, the new scenes are mostly well-judged, the subtle effects work well and the story is accessible to non-readers. One thing that will be interesting to see is how the show handles the expansion of the cast: by the end of Episode 2 we're two hours into the story and we still haven't even met Varys, Renly, Littlefinger, Lysa Arryn, Barristan Selmy, Samwell Tarly or other iconic characters from the books. How the show is able to juggle these new characters with the elements introduced in the first two episodes will be key to its future success.
More in-depth thoughts, especially on the actors, to follow.