Banks can be a kind of hit or miss at times, but I would still recommend reading all of them simply because it's not his writing so much as the world building I found most interesting about The Culture series. He creates this fascinating post-scarcity, post-species (i think), post-gender kind of society and then uses different characters from different walks of life to sell that society to the reader in the form of The Culture's recruitment process. In a way, the books become a kind of allegory for a Culture recruitment process of earth, I guess.

But also I think there's only couple books that really callback to each other so if you're not feeling one book move on and then come back to it later if you're more interested in The Culture's background.