GtrsRGr8 Christopher Hill is one of the great historians of the English Civil War period, but some of his work is controversial among later scholars. The book on Milton was originally published in 1977, see his obituary in the Guardian for some more information about the disputed aspects
http://www.theguardian.com/news/2003...ies.obituaries. Personally I considered it an absolute bargain at its original price of £2.99, when I bought it the other week, though I have not yet started it.