It is a fantastic book! And the setting of the film is different, but the story is surely the same: an emotionally immature protagonist gets swept up in an ever-expanding and quasi-supernatural game. The emotional crimes he plays out on others are played back on himself through this game, causing him to eventually achieve self-realization through a sort of emotional catharsis and resurrection (metaphorically in the book, quite visually in the film with the white suit and the graveyard and all).

Replace Greece with San Francisco and the sexual crimes in the novel with the film's emphasis on corporate greed. Still not convinced? The icing on the cake for me is the fact that both film and book end identically, hanging on a moment of choice in a situation which leaves it ambiguous if "the Game" is still ongoing.

I don't think Fincher really nailed the movie the way he did with Seven and Fight Club, but the connection to the Magus seems obvious for another reason as well: the weak points of the film start making sense if you think about it as an adaptation. The major point of the Fowles novel is in its Eliot quote that, "the end of all our exploring will be to arrive where we started, and know the place for the first time." I don't think the film is as convincing as the book in part because the romantic relationship it uses to do this is incidental to its preoccupation with corporate greed and is not very believable. But the intended structure helps explain some of its weaker dramatic moments, the biggest of which for me was seeing Michael Douglas running around a corporate cafeteria with a gun shouting about the need to protect his employees and their pensions.

The fact that it was not credited as an adaptation pretty much ruined the movie for me-- as I was watching it, I kept thinking "This is just a rip-off of The Magus".

As an adaptation, the film was quite good. As an (alleged) original work, it was a total failure.