Apparently there is some debate as to whether or not this is the first death metal album. I haven’t head the other contender myself, and cannot speak to that. I also don’t know mid 80s Thrash enough to speak to it. Also, I’m no genre purist, so I’m not sure I care for anything other than assessing this record as a historical document.
Whether or not it’s the very first death metal album, it absolutely establishes all of the genre conventions and for that it is extremely important. The genre may be named after this band, after all. (Whether or not it’s the most important death metal album is another story, and I don’t know the answer.) As metal, it’s fairly unparalleled in its extremity (for its era) and makes some of the more famous Thrash metal bands sound rather tame in comparison.
It’s also impressive that this way made by essentially one man (two men, really, but one did most of the work).
It’s certainly one of the essential metal albums of the 80s, though I don’t know how much I will listen to it in the future, given that it is one genre.