None of the books have a sympathetic protagonists. These are people who are morally and culturally so remote that you will almost never feel sympathetic for them. Some are straight up genocide for hire agents. Other are sexual perverts encouraged by the limitless nature of the power granted by they belonging to The Culture. Another few are neurotic messes. Curiously I find the stories and books that are lead by the Minds to be the most compelling and empathetic to the human condition. The most aliens of aliens are also usually way more sympathetic than the humanoids. You got to understand that Banks projected on The Culture the best but also the worst of Eurocentric (particularly English) colonialism, and with it all its anxieties and fears. Sometimes critically, sometimes not so much. This are not Americana pulp fiction Space Operas or young adult action packed dystopias. But more post-modernist elaborations on the fringes of human experience, or sentient experience altogether. Definitely an acquired taste and not meant to be read with a turned off brain.