The Player of Games
This is commonly recommended as a good entry point to The Culture book series which envisions a quite utopian humaniod inter-galactic civilization. In the Culture, humanoids and AI machines live together essentially without laws, currency, or scarciity. Although the Culture is largely utopian, adjacent civilizations are not, and the Culture often tries to make contacts with such civilizations to make them more compassionate and just. This book centers around a renown game player from the Culture who is sent as an envoy to an empire build around a type of game. Through following this envoy we experience the jarring differences between the two societies, where the more "barbaric" one bears many similarities to the real world.
Full Review