The first Culture book Iain is still finding his feet with the series so it's skippable if you didn't like it.

Also the series doesn't have to be read in order as they are mostly self contained stories although there are references to events from previous books they are very high level, in passing and pretty much spoiler free.

I personally love the universe Iain created for culture, so the books are as much about luxuriating in that than anything else. It's Hobbiton in space IMO. Some of the stories are a little obvious and some are a little overcomplicated but they are fun.

LeCarre is a wonderful writer, he excels in writing engaging and believable but average people who perform mediocre selfish acts rather than the exceptional performing miracles against all odds yet are somehow still boring people. There's no Jason Bourne or James Bond here. I would think of it very much like Slow Horses if you have read any of those?