In my opinion, the second game is easily the best in the Layton series.
Story: 4.5/5
Professor Layton's Mentor is murdered, presumably by the Elysian box which has gone missing. Layton and his assistant Luke take a train ticket they found in his mentors room and chase after the box. The game then takes time carefully setting up the pieces for the final event, and often cause you to wonder "what could possibly be going on". All the secrets of the Box will be revealed, and we are treated with one of the most touching endings ever seen. The ending of this story alone makes it the best in the series... however the story isn't quite perfect. There is one incident that makes me wonder if Layton is really fit to be a caretaker (*cough FLORA *cough). It is this little issue that keeps me from giving it a perfect score.
Graphics: 5/5
The art of the game is very warm. Yes it's a cartoon, but it's drawn in such a way that makes you think "maybe these places could actually exist". Then you come back to reality and no, it's just a pretty picture. The characters are all well drawn; I don't know what it is about Layton games, but they have some fairly odd looking character designs (still well done, but odd). There are also some backgrounds and environments in the game that are beautiful and make you want to see more, wishing you were not just stuck on fixed paths.
Sound: 4/5
The music and sound of the game is great but its puzzle song is nothing we haven't heard before. This song plays on a continuous loop while you are solving a puzzle, but it is pleasant to listen to (thank goodness). I would have enjoyed some different music during the puzzle segments (like what they did near the end of the Last Specter, but that game was 2 years after this one), but the music did beat out the first. The voice acting in this game is also wonderful, and most of the characters sound how you would expect them too. The best music though is by far the woods near the end of the game, it's so soothing and it fits the area perfectly. Had they tried to experiment with the puzzle songs earlier in the series, the sound probably would have gotten a higher score.
Gameplay/Control: 5/5
The entire game uses the touch screen, but it works perfectly. There are times I was wishing I could push a button to bring up the menu, but the game is simple and that's one of the best things about it. The puzzles get really challenging and are a great work out for your mind. There are a couple puzzles that are a little wordy and take a few read throughs to know exactly what you are looking for, but overall it's perfect and you know when you screw up it's because "you" did something stupid. The minigames are also great in this one with a camera you have to rebuild from scratch, pictures where you have to spot the differences to unlock new puzzles, a hamster you have to whip back into shape (WITH TONS OF WAYS TO COMPLETE THE FINAL CHALLENGE), and tea time where you combine ingredients to make tea as well as try to figure out what tea suits each stressed out person. There is also a diary you pick up later in the game which you gain keys for after completing certain puzzles, which reveals more back story behind the ending. It's simple, but it's fun if you enjoy challenging yourself.
Content/Replay Ability: 4/5
The problem with all puzzle games: if you solve them once it's pretty easy to remember the solution. This isn't a game you'll what to do playthrough after playthrough of, but with over 130 puzzles in the main game it will only take a few months before you forget most of them. The game also has tons to unlock, which might prompt you to play the game again just to get a better score and unlock everything. As in every Layton game, there are the weekly Wi-Fi puzzles (about 30 more I think), as well as the 5 rooms that will drive you insane. These five rooms are filled with the HARDEST PUZZLES IN THE GAME, and can have you tearing your hair out for weeks as you try to solve them. The game gives you plenty to do, and despite the one flaw of all puzzle games, you're bound to forget eventually.
Verdict:
Professor Layton and the Diabolical Box is my favourite game in the series solely because the story. It might have just been the things I was going through at the time, but I found the ending incredibly touching. That and the minigames are pretty much the only things separating it from every other game in the series, but if you enjoy professor Layton you kind of have to pick up this game
Recommendation: 5/5 If you like puzzle games and mysteries (or even if you don't care for mysteries) pick this game up, it's well worth it.