Consider Phlebas is the first book in Iain M. Banks long running Culture series of novels. It falls somewhere between a space opera and a travelogue to my mind.

There's certainly no shortage of action throughout the novel. It's pretty fast paced from beginning to end. But at the same time the story meanders a bit to show us the diversity of cultures in this universe.

It also has a strangely negative skew (at least by the standards of most SF)in that you could say the moral of the story is you probably won't make any difference in the long run.

There is a huge war being played out in the background of this story, but we are (deliberately I assume) kept at a distance from it and don't really feel the effects of the devastation that's going on. While the protagonist and those in his circle are driven by elements of that war, they also exist in their own bubble. We feel their concerns and their risks quite personally and yet in the end it's not clear that their actions actually changed anything at all. You won't feel that until you've finished though. While you're reading everything seems urgent and important.

The only area where I feel the novel slips (and thus loses a 5th star)is in the motivation of the protagonist Bora Horza Gobuchul. Banks sets up the Culture as such a clearly Utopian thing and their enemies the Idirans as sufficiently repellent that it's actually quite hard to buy into Horza's dislike of the Culture or his willingness to work for the Idirans.

It is addressed several times during the story but never in a way I found convincing. The Culture is just too perfect. Now of course in real life people frequently hold on to irrational, illogical and self-contradictory views. But ironically that doesn't work nearly so well in fiction.

It's a must read I think, but a flawed one.