A poor man's, or shall we say poor little girl's L.A. Noire.
The idea of an American Girl-based game sure seems 'swell in my opinion, especially a one set in Kit's 1930s (think Mafia, Godfather and all that Great Depression stuff) era, but the problem is that the way they executed this game for the DS seemed kinda' clunky, more so if a player from the intended target audience was to beat the game. Like in most detective games, you'll have to pick up clues, which is a chore given the low-res graphics and lack of an indicator of sorts to tell you whether you can interact with it or not.
Another complaint is that the player and ped animations seemed a little bland, like as if Miss Kittredge was the newest Asimo prototype or something. The DS may not have the raw grunt of it's 3D-enabled successor, but I'm pretty sure that something better can be done in that department.
Other than this and a few other minuses such as the lack of Wi-Fi multiplayer ala-Julie Finds A Way, some of the best bits in this game was that of the Kittredge household being recreated in full 3D, albeit pixelated and low-poly. You can dress up Kit in some of her period dresses, which were based on the ones seen in the original books, and can be bought as outfits for your doll.
To wrap things up, Kit's Mystery Challenge isn't really that of a bad idea, it's just that the developers threw in something that's too rushed out to be considered bearable.