Marketplace
Been waiting for this to go on sale. There are IAP, but without it you can finish the game. To get the complete puzzles or costumes for the main character, they come in two bundles: $22.99 and $12.99. (All of the information is what I've collated from reading news articles.)
I've noticed other apps have been mentioned on sale here on Ozbargain, and the page to that is here:
https://play.google.com/store/apps/collection/promotion_3002…
If you are a big fan of Layton games, maybe consider giving this a miss. I've played the whole thing and its pretty bad.
The plot is composed of 6 barely related stories, and there is a very minor overarching plot. The puzzles are generally crappier as well, Level 5 had to replace their puzzle master from the earlier games apparently.