The quick and dirty recommendation guide (pick as many +/- points as you like and make up your mind if it's worth buying):
+ strong narrative
+ outstanding sound and visual presentation
+ responsive, intense and simple combat
+ nightmarish horror atmosphere (without jump scares)
+ superb voice acting
+ frightening and well-designed end bosses
+/- combat lacks complexity and may be too simple for some
+/- no replay value (it may have for a revisited experience)
+/- bit short, which is compensated by fair price and gameplay without tedious and lengthy grinds
+/- high stylized presentation of events and plot may not be everyone's taste (totally mine, though)
- gameplay doesn't offer much variety
- not much to explore apart from lore stones telling you about Norse mythology (which is quite important, however!)
- lack of variety in enemies and their appearance

The details:

Hellblade tells a story about suffering, sacrifice, darkness and endeavor. Following the story of Picts warrior maid Senua, you embark on a nightmarish and mind-twisting journey to Helheim, to save a beloved one’s soul. However, for Senua, many things aren’t what they’re supposed to be, for she’s suffering from severe psychosis. While you often can’t decide what’s real and what not, you must overcome many obstacles and enemies – the latter seemingly coming right out of Hel(l).

No other game, up to this point, managed to devour me – getting me so immersed – like Hellblade did. This game just pulled me deeper than any other game has accomplished in recent years, and I, mentally, switched off everything else around me and Senua’s reality became mine. The sound design and visual presentation is outstanding.

I was always a fan of non-linear storytelling and Hellblade totally nailed it. Its presentation is intriguing, captivating and keep you ever so interested in what happened (to Senua) and how everything will turn out.

As for the gameplay I was kind of surprised of what they came up with: There's a level where there is nothing but darkness and you have to find your way out, without fighting, only using your senses, as Senua's reaching out with her hand to frisk her surroundings, or running from one light source to another to not getting devoured by darkness. In other parts, cynically spoken, you could call it 'walking simulator', but, as for myself, I was so immersed in the world that I didn't mind. It doesn’t deliver any boredom even when ‘nothing’ happens.

There is one thing to explore off the main paths, however: Lore stones. These stones – telling you about Norse mythology in appearance of an old friend – are optional but critical in further expanding on the whole game’s story. At first one might not see the entangled meaning of Norse mythology and it seems rather random, just to give this game a Norse touch although you're not playing a viking heroine. Certainly, Vikings are involved in the story but that doesn’t necessarily explain why you keep hearing stories about the Northmen. But keep your wits about you and you’ll come to realize the importance of those stories.

I also enjoyed the combat, although it lacks complexity and deep mechanics. So, what is to like about it? Its responsiveness and simplicity made it a blast to play. It is quick, brutal, intense and it just works without any clumsiness. In that regard it is sort of 'flawless', straight on point. Don't expect anything near like Dark Souls, though.

Visual clues were used in a clever way and weren't spelled out boldly for you with exclamation marks, compass needles and the like. Even in one given situation where acting under pressure and time limit was required, I managed to find all the necessary clues at the first try without said compass needle or other HUD markers pointing out where to go – there are voices telling you to "focus" or to look in another direction. The lack of (almost) any meta information fits the theme of the game and it is an enjoyable change in a video game. That being said, there's no "meta game" telling you how to do things (apart from the game options menu). No HUD, no text boxes or pop ups. Everything you need to know to beat the game is offered by the environments and from 'within' the game.

It absolutely has become one of my favorite games by now.