Great artwork and great puzzles!
There are several "layers" to the puzzles, and my kids and I are only going through the first layer as I write this review, but it's great so far! As in the examples, it's mostly look and find, but there is more "puzzling" puzzles alter, plus I have been watching the kids pass over clues to the overarching puzzles. This is very much in the style of the Usborne Books puzzle books "Knight's Quest", Dragon Quest", et al.
I bought the PDF, and was able to print out the puzzles 11"×17" (approximately A3) in glorious colour, and it's great. This is one case where "the medium is the message", and I don't think the native PDF would be as enjoyable, unless you have a decent tablet.
With that out of the way, I also want to say how great it is to find an activity book like this, online, in PDF for a rainy dat activity for the family.
My only complaint is that Planet Urf hasn't released their "Where's The Mermaid" book on DTRPG yet!