Some Games are Played with Other Players
Video gaming has evolved from a single-player environment to multiplayer modes where players cooperate or compete. Especially with the Internet, gaming is an increasingly social and communal experience.
The author doesn't subscribe to the notion that single-player is going to disappear - but that "number of players" is an option to be considered in game design.
The author rehashes some of the information from earlier chapters about the properties of multiplayer games (competition, collaboration, esteem, etc.) but doesn't seem to add anything new to the exploration.