Best Dark Souls 3 DLC.

In all seriousness Hollow Knight is a metroidvania with close combat and profound storytelling.
The game starts off as an intriguing adventure into the depths of the unknown city. Everything seems like a fairy-tale. However as you progress through the game, you uncover deeper, darker lore and various bizzare characters of Hallownest.

The narrative of this game strongly resembles that of Dark Souls 1 and 3 with the style of its dialogues; lore, implied through hints and items; and the overall grim "knights and mages" setup. The metroidvania part of the game bonds well with the storytelling as you will explore the world and become stronger.

Exploration is enjoyable for the most part, but occasionally platforming seems like harder levels of SuperMeatBoy and the difficulty may skyrocket from location to location.
The combat-mechanics are complex. 10-15 hours into the game you keep learning something new. There're also some peculiar details, like you can overequip your socket-items, but you will receive double damage.

The enemies deserve their own mention, as the bestiary is vast. Plus I was in for some surprises, when I noticed, that some enemies (usually - weapon wielders) can be parried, if timed correctly.
The artwork is clean and gorgeous. The levels look rich and have great variety. The sound design is simply amazing in all aspects.
And last but not least, the game has so much content, I can't see an end to it. 21 hours in seems like early mid-game.

Overall I am astonished with the scale of this project. Even though platforming is not my thing and it enrages me, the game keeps envoking positive emotions as well. In fact, Hollow Knight overachieved my expectaions, and I am looking forward to seeing more games from the awesome dev team!

tl;dr: game is great, try it!