Milton

1. What Blake said about Milton:

We're led to believe that Milton was Blake's primary teacher and inspiration (aside from the Bible).
"Now my lot in the Heavens is this, Milton lov'd me in childhood and shew'd me his face.
Ezra came with Isaah the Prophet, but Shakespeare in riper years gave me his hand."
(Letter to Flaxman in 1800; Erdman 707)

From The Marriage of Heaven and Hell we read:
"For this history has been adopted by both parties
It indeed appear'd to Reason as if Desire was cast out. but the
Devils account is, that the Messi[PL 6]ah fell. & formed a heaven
of what he stole from the Abyss
This is shewn in the Gospel, where he prays to the Father to
send the comforter or Desire that Reason may have Ideas to build
on, the Jehovah of the Bible being no other than he, who dwells
in flaming fire.
Know that after Christs death, he became Jehovah.
But in Milton; the Father is Destiny, the Son, a Ratio of the
five senses. & the Holy-ghost, Vacuum!
Note. The reason Milton wrote in fetters when he wrote of
Angels & God, and at liberty when of Devils & Hell, is because he
was a true Poet and of the Devils party without knowing it."
(Erdman 34-5)
In this passage Blake may be referring largely to Paradise Lost.

2. The Book of Milton:
Blake had some problems with his primary teacher, as is shown in MHH.
After Blake's awakening experience he knew how to address the matter more closely
than he had in the earlier poem: he called Milton back from Heaven (the first we
know of since Jesus).
There were six women in Milton's life, three wives and three daughters; they enter
into the Book of Milton.  In the Book of Milton Blake had Milton come back and
perform a task here on Earth somewhat like the far larger ministry of Jesus.

3.  Much can be found published in the Internet about Milton:
This Blog has a large volume of material, much of it inspired by the Blake Primer
or the Website.
More recently the Blakean-Bible came into circulation.
And there are many other writers and interpreters of William Blake.