Ignore the bad reviews, they are just childish people who are sore about not getting it all.
This is a great game, it is everything you expect from the usual Prof Layton games.
DO NOT be put off buying it because of the "missing game". Having played 'London Life' it isn't that great. It isn't the acclaimed "100+ RPG". It takes much less time than that and is a joke to call it an RPG. It could easily be mistaken for a Gameboy colour game. You are not missing anything.
If you want a good Professor Layton game with the same great puzzles as you have come to expect then buy it, don't hesitate.
If you are thinking of taking the risk of buying an American copy, don't 1) The game really isn't worth it. 2) There is no garuntee it will work on your DS (the bad reviews fail to mention this) 3) I'm guessing you are buying this because you want a fun puzzle game? yes. If you want to have an RPG buy something that was made to be an RPG, not something stuck into a bundle.
If you want an RPG that DOES last a long time, then buy this AND Skyrim, or pick up a Final Fantasy game. Just don't be put off that 'London Life' isn't here, it really isn't worth the hassle.