I only really know the Songs of Innocence and Experience by Blake, and the Marriage of Heaven and Hell (required reading, but I'm fond of them :-D), I never really worked up the courage to dive into the longer stuff! But I figure all that stuff about Blake seeing himself as a prophet, and challenging established views (for example, Innoncence isn't necessariy a desirable state in the Songs, depending on how you read them, Experience has its own value)would be something John might be quite drawn to.

Uh. I will stop rambling about Romantic poetry at you now. Former English student :-D