Internet sources

http://www.luminarium.org/sevenlit/milton/

A website dedicated to English literature from the Middle Ages up to the 17th century. Here you’ll find links to all the online texts of Milton's work and a lot of additional sources.

http://www.sparknotes.com/poetry/paradiselost/

An extended treatise on Milton’s epic. It contains a very elaborate summary and analysis of characters and themes. Very useful.

http://www.sparknotes.com/home/english/

Sparknotes is a study guide made for (American) high-school students by students from Harvard University. The website contains a lot of English literature from every period. Each work is discussed in detail, and in many cases, there is an online text available. The information itself is very good, but the advertisements make it a bit annoying.