Single player board games
 

I have Sudoko books and I am not sure whether it is fun to play Scrabble alone !

Can someone list some other board games which can be played/enjoyed alone ?

I would love to go ahead a purchase some :)

EDIT
No computer games please !

i'm fond of the patience card games and there are several suite, xpat, kpat and python. kiriki is a yahtzee game, as is openyahtzee. othello, or reversi is an interesting game. knetwalk is a join-the-monitors-to-the-power-supply game. mahjongg is also a nice timewaster.