Many people feel "consider phlebas" to be one of the weakest in the culture novels, though I really like it as an intro to the series. A big reason the abominable intelligence recommended starting with the second book, player of games.
The tone and perspective shift WILDLY through the series, so I'd highly recommend picking up one of the other books and giving it a try.
If it makes you feel better:
spoiler
The book ends with everyone dying a pointless death because war sucks.
Lol, same