A well-summarized introduction to the psychology of video games in gamasutra:The Psychology Behind Games By Anders Hejdenberg. The author first presents idea like Maslow's pyramid as well as basis concepts emerging from Roger Caillois or Csíkszentmihályi's (pronounce chick sent me high yeeeeee, this is true!). Then he describes the consequences for game designers. Event though it's a brief account, that should be seen as a good introduction for game designers.

I just put here the conclusion which is obviously interesting from a user-centered point of view:

We have to realize that making a great game is not about which features and components to add – it is about what those features and components do for the player. We have to learn not to underestimate how important certain aspects of the design are to the player – for example, difficult controls alone can transform any great game into a meaningless activity. We have to remember that we do not make games for ourselves – we make them for the player.

Sometimes game designers tend to forget this basic rule, they design for an audience not for themselves.