Hi Edwin,
Since this is considered one of Blake's major works, you can find full-length books analyzing it as well as articles in our literature databases and even general databases. I suggest starting off by retrieving the books we have in the library such as "Wiliam Blake's The Marriage of Heaven and Hell" edited by Harold Bloom on the 3rd floor call # PR 4144 .M33 .W5 as well as "The Heaven and Hell of William Blake" at PR 4147 .S2. A librarian can help you locate these on the 3rd floor. You can also look at additional titles nearby that contain criticism of Blake's works.
This work is also covered extensively in the major serial criticsim series "Nineteenth Century Literature Criticism". We have these in print in the library - a librarian can help you locate the particular volumes that cover The Marriage of Heaven and Hell but you can also find digital versions of much of this content spread across the databases Literature Criticism Online and Literature Resource Center. You can access these databases from the library homepage alphabetically under "databases A-Z". Start with Literature Resource Center and use the "Works" tab to find articles. Try typing "blake and marriage and hell" or similar in the search box and you should pull up a number of articles under the "criticism" tab. Addtiionally, try the database Academic Search Complete under the "A" tab and type a similar search and you will find full text articles.
If you need help searching or want to expand to other databases, stop by the library and speak to a reference librarian or call the library. Keep in mind that if you are accessing the databases from home you have to have a working password with you N#.
Best
