I got this game in a bundle and played it primarily for the cards, however, I came to realize that it was actually a charming hidden-item adventure point-and-clicker. I also recently played Nightmares of the Deep: The Cursed Heart, and I think I prefer Nightmares more if I were to compare the too. It is difficult to weight the two fairly though, as Nightmares has more game mechanics like verying minigames and the skip/hunt function.
Oknytt is a darker art, not necessarily grim but moreso noir style (think Don't Starve atmosphere if you're familiar with that). You play a weird little creature with amnesia and have the power of the four elements in the form of stones. For example, in some scenes you can use the fire stone to make a burnt out fire pit come temporarily back to life. While most of the stones in each scene gives a purely aesthetic effect, some puzzles require the use of the stones.
There is no hint function (but there are two guides available that basically feed you 100% achievement for the game) and the puzzles are not necessarily challenging, however, many of them require you to backtrack and combine items in your inventory.
The music is decent and the visuals are appropriate for the atmosphere created by the game and storyline, however, I personally find the narrator to be a little annoying. When he narrates the main character, you can hear him switch into a child's voice and something about it annoys me (may not be as big of a deal for you).
Price-wise, I would say to spend the extra $ to pick up Nightmares if you're really into adventure point-and-clickers. This game is also not that long (5 chapters I believe), so I think grabbing it at a lower price would be most advisable.
It is a good game though, although some of the puzzle solutions may not be immediately obvious or intuitive.