The Golden Compass wasn't even two hours long. That seems pretty remarkable for any blockbuster these days, and especially one adapted from such rich source material (by contrast, the shortest Harry Potter film is 2 hours 10 minutes, and that was from a book split into two movies!). You just can't do justice to these books in that space of time. There's an array of characters, a world filled with magical creatures, and various machinations pulling the plot strings together. Basically, it seems perfectly suited for a TV adaptation, if they take their time with it. The plan is for 8 episodes (with a report of five seasons being the goal), and you'd imagine these will be somewhere between 45-60 minutes in length. If the entirety of Season 1 follows the first book, Northern Lights, then that's 6-8 hours of screentime in which to do it. There's no need to rush things, or make unnecessary changes to expedite the plot.