From somebody who knows nothing about the first film..

Rating: 8/10 (1 November 2015)

...but has thoroughly enjoyed the second one since it came out in 1987. From reading other comments apparently history has been rewritten in relation to the first, but I can't speak to that. Let me just say that if you haven't seen the first one the second one fills in enough details that you know what is going on.
The film starts with Ash and girlfriend Linda taking a romantic weekend trip to a cabin. It's a cabin that Ash knows about, but says he does not know the owners, thus he really doesn't know their whereabouts. He says they'll just claim to have gotten lost in the woods if they show up. The cabin is actually where Professor Knowby brought the recently discovered Book of the Dead. We know this because Ash finds the tape recorder and plays Knowby's entries. On the tape Knowby speaks aloud the words that are supposed to resurrect the evil dead - those evil spirits that inhabit the forest and world around us. Once brought to life they can apparently manipulate objects and possess people at will, in search of a way back into this world via possession and a way to harvest souls for hell. Those spoken words do their work, and the evil dead are brought back to this world. Well it is nighttime, and since that is when the evil dead are active they immediately begin to make Ash's life a living hell.
Meanwhile, Knowby's daughter Annie is on her way to the cabin with more pages from the Book of the Dead where she thinks her parents are doing research. She has with her a research assistant, and two locals who show her a way around the destroyed bridge that leads over the canyon to the cabin - a bridge destroyed by the evil dead to trap Ash where he is.
There is confusion at first as Ash fires a shotgun through a closed door when he hears the four trying to enter the cabin - considering what he's been through up to that point that's no wonder. Likewise, at first Annie looks at the blood and destruction of the cabin and thinks Ash killed her parents. However, it is soon obvious what the real enemy is here, one you cannot see or hear, one that can possess anything, anyone, or even just part of a person. It can make the dead appear as they did in life, it can make the living appear as demons. One particularly creative thing done here is that you see things occasionally from the evil spirits' viewpoint as they rush through the woods, making an awful roaring noise, headed towards the cabin.
The action and the chaos just never lets up from the time the forces of evil first attack the cabin. It's hard to describe, and I know it sounds strange, but there is enough tongue in cheek humor merged with some really riveting horror, that you don't feel completely drained from the intensity of it all. For example, when you have both a possessed lamp and a possessed stuffed deer head laughing at you, things get both so horrible and funny that you feel you are watching a satire of a horror film. Only the very end confused me a bit, and maybe that is because I haven't seen the first film. I'd recommend it as horror well done in a different and creative style.