A fantasy book that I read between 2000 and 2010 (probably in the middle) that was published around that time too, that I don't remember as being particularly well known, revolved around a boy travelling through different worlds trying to find his way back home (maybe after having been thrown forwards in time to the present?) who discovers that life is controlled by mysterious robed and hooded figures playing board games. They have a big computer that checks rules for them (I think), and the story culminates in the boy breaking through the windows into the room where they're playing and then ... (I don't remember).
Along the way he meets a girl whose home planet is a hot desert with lots of dangerous animals, and a titan (?) who has been chained to a rock for eternity doomed to have his eyes pecked out by crows.
This last point reminds me of the Keys to the Kingdom series by Garth Nix, but I'm certain that the book I'm thinking of isn't in this series. It was very much a standalone.
Very much a long shot with this description, I know, but it's been bugging me for years now and I'd really like to know what it was! It's been useless trying to google it because I just keep on turning up stories about D&D.