What makes John Milton's "Paradise Lost" so unique to other epics?

This is a difficult question to answer because, in the truest
senses of the word, each literary work, including Paradise Lost, is “unique”
(one of a kind). If any work is examined closely enough, any work will necessarily seem “unique”
unless it is simply a carbon copy of some other
work.

Paradise Lost is highly distinctive in
the history of epic poems partly because it uses the English language to combine classical
literary influences, especially the Iliad and the
Odyssey, with fundamentally Christian ideas and a fundamentally Christian
message. No talented poet before Milton had ever done quite the same thing in English, and no
great poet has done anything in English in quite the same way
since.

Also making Milton’s epic highly unusual, both before his era
and afterwards, is the way it draws on the Bible so explicitly for so much of its plot and
characterization. And yet Milton also, of course, expands enormously on the basic Biblical story
– another feat that few poets in English have attempted since Milton’s
time.