Disclaimer: I have yet to finish the game. I felt compelled to write a review, however, because the game is a joy to play.
Edit: I have since finished the game. While the puzzles get tough if you are playing the hardest difficulty, it remains a very good game from beginning to end.
At its core, Bilkins' Folly is an adventure game, themed around treasure hunts. Everything is tied together by the protagonist's search for his missing family members, taking him to explore the game's world bit by bit as he tries to follow their trails. The plot isn't very serious at all in the moment to moment scenes, instead providing humour through most interactions.
You'll be solving puzzles and riddles of all kinds, while also dealing with a plethora of mini-games (fishing, lockpicking and more). Checking maps while walking around with your loyal dog is just so much fun, and the wacky comedy of the world and its characters makes for a great backdrop to your adventures.
There is no combat, but you still have an ever-expanding arsenal of tools to open new routes around the islands you'll visit. Your dog companion also learns new tricks along the way, and you'll need to backtrack to unearth every secret on each island (it's surprising how much you can find by simply exploring, with very little in plain sight).
The music is very fitting, and generally I find the sounds to work really well in creating a fun-loving atmosphere.
Completionists could find the game slightly frustrating, as there are a lot of small things to find, and some of the puzzles can get challenging, but overall, the game is not hard.
The game might not be perfect, but it's really well-designed, which I find a bit of a rarity these days. If you like treasure hunts and puzzle, you owe yourself to give this one a go.