Excellent, but more of the same
The third Layton adventure again puts the player in the shoes of the puzzle-solving archaeologist and his eager young apprentice. You'll navigate an "anime-Europe" version of London via the DS stylus and tap on the screen to hunt for clues and talk with other characters. The plot unfolds through a combination of spoken and written conversations and animated cut-scenes. And, of course, puzzles.
Layton is basically a collection of about 150 logic puzzles wrapped up in a mystery setting. The puzzles have been refined since the first two games - gone are the Queen's Gambit and Knight's Tour series of chess puzzles, move-the-matchstick puzzles have been almost entirely eliminated, and there are only a handful of sliding block puzzles. This seems like a conscious effort from the developers to both inject some variety into the game and also eliminate a significant source of frustration, and it's good to see that some serious thought is still being put into the game.
On the downside, if you've played the first two Layton games, you've played this. It takes about a dozen hours to play through the story, assuming you make some effort to locate as many puzzles as you can. There are bonus puzzles that can be unlocked by completing mini-games, just like before, and you can download weekly puzzles. On a personal level, I found the London setting to be a bit unsatisfying - it just seems so small compared to what London really is, and felt more like a generic village than a proper city. I actually much preferred the train setting from Professor Layton and the Diabolical Box, as it had a certain air of mystery or romance, a la Murder on the Orient Express. By the end of the game, I had lost interest in the story and was just playing to be done with it.
Your experience will certainly vary, and if you tend to play in smaller chunks rather than marathon sessions, then The Unwound Future may hold up better for you. In the end, this is still a great Layton game, and if you loved the first two you'll probably derive at least some enjoyment from this. Just know going in that it is more of the same, with no radical changes or improvements.