Chalk it up to the fact that digital Sudoku isn't terribly difficult to replicate to begin with, and add in the fact that some handy videos of Ms. Vorderman actually explain the basic concepts and a few handy tips for newcomers and you have a game that at the very least, gives you a way to play Sudoku on your PSP with minimal fuss. The whopping one ambient track and bajillion permutations of the game sort of handle the rest, even if learning the controls will take a bit of getting used to.
Since I'm clearly not answering the question of what Sudoku is, I'll at least offer up an explanation of the grinning gal on the cover. She isn't known in the least here in the US, but in the UK, Vorderman has managed to garner quite the following -- for good or ill -- as the host of Countdown a math-based quiz show that's helped the enterprising lass to pocket the equivalent of about $5 million here in the US. It's seriously money, but if nothing else, she actually helps newcomers (in a quasi-condescending way) to learn the ropes.
The game itself is... well, it's there. Presented in a handful of different modes, including ones where you can challenge Carol's time on a particular puzzle or work your way up in a "Career" Mode, plus some basic Challenges and of course the all-important Classic Mode with assists, the game actually presents a healthy number of options with at least a vague sense of progression. Hell, you can even make your own puzzles and have the smarty-pants PSP solve 'em for you if you'd like.
As mentioned before, the controls take a little getting used to, if only because all the face buttons do something. Triangle backs you up one step no matter where you are on the board, Circle will temporarily assign a number to a space (which is absolutely necessary for solving the harder puzzles), X actually places a number and Square kills that square. There are two control options, but the only difference between 'em is the fact that you can either set a square to be a toggle with the X button that then brings up the 1-9 number picker or you can have the shoulder buttons do it all the time while you scoot around the grid with the d-pad like a pro. Either way, it just takes a bit of learning that default yes/no buttons don't really do that to get a handle on things.
In stark contrast to the approach taken by the folks at Sumo Digital while crafting the surprisingly good Go! Sudoku, however, is the presentation, which sort of scoots by on the basic presentation of simple languidly meandering numbers as a backdrop and simple stills of Vorderman for the menus. It's not flashy, it's hardly PSP-pushing in any way, but hey, it's Sudoku, there's only so much you can do before it gets insane. At least the videos are well encoded and Carol's sharp essssss sounds kinda make me all tingly.
I'm not knocking the game for its presentation. What it does, it actually does very well; there are plenty of options for single-player that both help you get better at the game and give you plenty to digest for quick play, and Carol's comments are actually relevant if you're a newcomer to Sudoku in general. Aside from the history lesson every time you start the game, it's mostly cut and dry (and a little pedantic at that), but at least it will help catch everyone up to speed. If you're looking for a PSP Sudoku game, congrats, you've found it. It won't sell systems or anything, but if nothing else, it does precisely what it purports to do: it delivers a ton of Sudoku for a reasonable price.