This film is a follow up to to Raimi's first film in the series The Evil Dead. Raimi's film uses the same protagonist, Ash Williams must once again overcome demonic forces in order to save his life. Raimi plays with the themes of hubris and what one will do when faced with a life or death situation. We see this element of hubris in Professor Knowby who's found the book of the dead and begun to transcribe it, but only to his death as his recording these spells has allowed for a demon to be unleashed in the woods that claims the lives of all but Ash and eventually send him back to 1300 A.D..
And when Ash cuts off his own hand after having killed his girlfriend Linda (twice) we see the reality of the desperation Ash is operating from in order to save his life. The film has essentially created its own genre combining horror elements with comedy in such a way that it becomes new. What we see in this film is the reality that evil forces are lurking and waiting for the help of humanity to bring them forth into existence upon the earth.
Raimi's film is quite clearly showing that it is the foolishness of man that brings forth such evil. The book of the dead is a piece of material that should be destroyed as its findings simply cause bloodshed and bring no life. So the professor knowing what he was reading perpetuates evil upon Ash and Linda by making a recording of the book of the dead. In this he has essentially damned anyone who accidentally listens to it and takes away the choice to read from the book or not. So, the real question here is, "Why would someone record spells from the book of the dead knowing they will bring death?"
