Consider Phlebas - Iain M. Banks
A high-speed action-packed tale, and also a serious one, treating a number of themes with considerable subtlety. As notable for the history and society it develops, as for its moral complexity; what appealed to me the most, though, was all the distinct and believable characters, empathetically portrayed with their own motives.

The one complaint I have about it is that all the fights and narrow escapes overshadow other aspects a bit, and may reduce its re-read value. Compared to other action novels, though, it stands out head and shoulders.