On March 17th for $4.99
Aksys Games is bringing the DS game 999: 9 Hours, 9 Persons, 9 Doors to life in the form of a visual novel on iOS. It's set to drop on March 17th and priced at $4.99 -- since it is interactive, you'll have some choices, sans puzzles.
While I don't want to outright spoil anything (although a four year old DS title is totally game), I'm not so sure about how great this would work without the second DS screen. Trust me when I say the dual screen mechanic is absolutely essential, and directly linked to the story.