This is, truly, a fantastic poem, in all senses of the word. It tells the tale of the Fall of mankind from Eden, including the story of Lucifer's Fall from Heaven to Hell. It's a story of rebellion, with Satan, surprisingly, as its hero, and a story of warning to mankind: behave, or this is what will happen. It is a story of grandeur, of titanic powers clashing, of direful curses and great councils and unmeasurable sorrow.
It's a poem that demands to be read aloud until your throat aches and your family think you are strange. It is thought-provoking - wouldn't you stand with Satan against a God who forbids to his followers knowledge, of all things? - and fast-paced and eloquent; it sheds light on years of literature, for everything from Mary Shelley's Frankenstein to Philip Pullman's Amber Spyglass responds to it; it's a real blockbuster of a poem, and the remarkable thing is, it was written over three hundred years ago. Really and truly, this is a poem that needs to be read by everyone. I know that's a phrase that gets bandied about a lot, but here it is true. Love it, hate it, be indifferent towards it - whatever you think of it, just read it.