If you know your Bible, Aeneid, Illiad, and Odyssey, you are off to a good start.
I had a professor whose approach welded historical narratives into the works we were reading. In the absence of a good Medieval or English Literature Professor, I'd recommend something like The Connell Guide [1] or the Oxford guide [2]. If you're looking for an all in one with very good marginalia and footnotes, I found the latest Norton Anthology series to be very good (and usually considered the academic definitive). You'd need to find the volume that has Paradise Lost in it, however.
I had a professor whose approach welded historical narratives into the works we were reading. In the absence of a good Medieval or English Literature Professor, I'd recommend something like The Connell Guide [1] or the Oxford guide [2]. If you're looking for an all in one with very good marginalia and footnotes, I found the latest Norton Anthology series to be very good (and usually considered the academic definitive). You'd need to find the volume that has Paradise Lost in it, however.
[1]: https://www.amazon.co.uk/Connell-Guide-Miltons-Paradise-Adva...
[2]: https://www.amazon.co.uk/Oxford-Student-Texts-Milton-Paradis...