I know ill piss of a lot of Planescape Torment fans here, but if you wanna write a book, write a book. A game requires interactivity that goes beyond that of fighting fantasy books.
That's not an unreasonable position, but IMNSHO the combat in PS:T was rather lacklustre, so without the story/writing the game would have been entirely forgettable. While I've seen the 'book' criticism before, I don't think I've ever seen anyone recommend the game for the combat (not that it comes up very frequently any more in general gaming discussions).