I sometimes take the No 43 bus to the University District to go to the bookstore there, and just to check out the joint .. and so that is what I did on Sunday.
There is a whole shelf of Soduku books. I am a Scrabble addict, but so far the Soduku bug has not bitten me. Per WIkipedia, Soduku was introduced in Japan by Nikoli in the paper Monthly Nikolist in April 1984 as Sūji wa dokushin ni kagiru (数字は独身に限る?), which also can be translated as “the digits must be single” or “the digits are limited to one occurrence.” The Times of London began featuring Sudoku in 2004.
The number of classic 9×9 Sudoku solution grids is approximately 6.67×1021 .. so players can rest assured that it will be a long, long time before they exhaust all the possible permutations !