The Culture novels are a set of 8 science fiction books set in the same universe as one and other. Each book is pretty independent from the other - this isn't a grand epic. There's virtually no continuity between stories or characters, though it's still a good idea to read them in order of publication.
If I have a complaint about the books it's that they are quite descriptive. These aren't the sort of books you want to be reading when tired. You can easily end up skimming a couple pages without really knowing what's going on. Calling parts tedious would be unfair since the stories are well told and quite eventful. Also, I generally prefer epics but not every book/series can (or should be) Dune. However, once you get more familiar with the Culture universe you'll find that the stories lack a certain level of drama/suspense simply because of how powerful the Culture is. You always feel like, in the scale of things, the events are pretty insignificant.
There are at least two great things about the books. First, I love how the story is told. It's often from multiple points of views and even different time frames. Most stories slowly come together. Think Pulp Fiction. At first its a little disorienting, but when properly executed (which it is here) I quite enjoy it. Of course, the main reason to read the books is because of the unique perspective it takes on science. The Culture is a utopian society. There's nothing evil about it, the AI isn't evil and there isn't a lower class no one talks about. Where most books/movies look at how science can destroy us, the Culture looks at how our lives would be if everything was perfect. Personally, I think this is a much more difficult thing to write about, and also pretty damn interesting (although, again, when everyone is all-powerful, it's hard to feel like anyone is in any real danger). Of course, there are other players in the galaxy and most of the books take place along those not-so-perfect borders.
Someone once told me that science fiction is all about the impact of science on individuals and societies. For example, Dune might not be considered science fiction because, while there's some cool technologies which do impact people (say, personal shields), the core of the story could be retold in a modern day setting with oil rather than melange. I'm not sure I agree with that; but I can tell you that when it comes to the impact of science on society and individuals, the Culture is pretty awesome. This is done in a subtle and natural way, no tech porn for the sake of tech porn.
Half way through i took a break and read The Algebraist, also from Iain Banks. It too is quite good. It very much feels like a Culture book, even though it isn't (same writing style and all). I've moved to the Hyperion Cantos by Dan Simmons. I can already feel this is more my type of science fiction. However, like I said, the Culture gets extremely high marks for tackling science from a relatively unique and refreshing perspective.