According to the stats, I played it for over 21 hours, which is about 5 hours longer than its predecessor. Which is pretty much what I expected.
And, erm, that’s it. It’s great Picross game, just like the first one only bigger. In terms of value for money, £7 for over 20 hours play is pretty good going. It’s a shame there are no bigger puzzles as 15×15 is a bit small, but still – minor complaint.