I can't find it online (do let me know - via the comments - if you can) which is a pity as it is a nice, breezy introduction the poem. It is, however, like the volume itself, devoid of the usual scholarly framework you might expect to find in a reprint of a classic: for that you'll need Penguin Classics' Paradise Lost or Oxford World's Classics' Paradise Lost. (I also hear that Longman's edition is very good.)
Pullman says in his introduction:
A poem is not a lecture; a story is not an argument. The way poems and stories work on our minds is not by logic, but by their capacity to enchant, to excite, to move, to inspire. To be sure, a sound intellectual underpinning helps the work to stand up under intellectual questioning, as Paradise Lost certainly does; but its primary influence is on the imagination ... I don't think that the version created by Milton, blind and ageing, out of political favour, dictating it day by day to his daughter, will ever be surpassed.