Great fun though poor story and ending
It is a linear FPS more than RPG though the character development is effective and easy to understand and do. I went for melee when I played it but it would be easy to play again as a wizard although I am not sure I have the interest to do that just yet.
The game is a bit short (took me a few evenings) although as I say it is FPS not a wide open RPG. Also the ending is rather poor. There are 2-3 possibilities for the ending but either way there is not even a cut scene at the end or any sort of reconciliation with the demon chick that is in your head for most/all of the game so it falls a bit flat at the end.
Just good fun really though; well worth a few hours.