What has happened so far in the first five books of Milton's Paradise Lost?
Paradise Lost opens, in accordance with epic convention, in the middle of the action (in medais res). Milton begins by setting out his aims for the work ('to justify the ways of God to men'), and invokes divine inspiration to be his muse in writing the poem. Satan and his host of rebel angels are in hell, on a burning lake, having been turned out of heaven for revolting against God. Satan uses his skills as a leader to rally his troops and summon a council to determine their next move. The fallen angels build a palace, Pandemonium, where the council will take place.
Book 2 opens with a debate in Pandemonium. The fallen angels differ as to what to do next; some favour war, others slothful inaction. Mammon, who sees Hell's natural resources with a materialistic eye, suggests they make the best of what they have. Beelzebub, though, sways the audience by proposing Satan's own plan, that thy adopt 'some easier enterprise', upsetting God by destroying what is dear to Him: Man on the recently created Earth.
Satan volunteers himself for the mission, and departs across Hell, reaching the gates guarded by the allegorical figures of Sin and Death - his own daughter, lover and son in an incestuous parody of the Trinity. He talks his way past them, promising them ample food once he can corrupt manking to his ways. He journeys across Chaos, the uncreated matter of the universe, and views Earth hanging from the vault of Heaven by a golden chain.
In Book 3, God in Heaven observes Satan's actions, and foretells their 'success' with the Son. Mankind will fall, but God, through his infinite grace, has granted Man free will and the ability to withstand temptation - just as Satan had. unlike Satan, though, Man will fall through deception, and can be redeemed through Grace. The Son offers Himself as ransom, taking Man's sins upon Himself. Meanwhile Satan reaches the outermost spheres of earth, adopts the disguise of a lesser angel, and deceives the angel Uriel into allowing his passage to Earth itself.
Reaching Earth, Satan is at first beset by envy and despair, but recovers himself enough to survey the scene of Paradise, in the Garden of Eden. In the form of a cormorant, he perches on top of the Tree of Life in Eden, and learns that Adam and eve are forbidden to eat the fruit of the Tree of Knowledge. This gives him a plan for their destruction. He is apprehended by two angels appointed by Gabriel to watch over adam and eve, as he speaks to Eve in a dream, tempting and troubling her. Brought before Gabriel, he is at first defiant, then flees.
The following morning, Eve tells Adam her dream, and he comforts her. God sends Raphael to remind Adam of his freedom to choose and the need for obedience, and to warn him of Satan's plan. Over a meal, Raphael tells Adam the story of Satan's rebellion.