Claire Tomalin thinks it's Milton.
I suppose that depends upon what thrills you. If prolixity and Puritanism (granted, a freakishly un-puritanical Puritanism), then Jack's yer man. But we at the Egg find more thrills in fourteen lines of Donne (we're thinking of the vastly underrated Holy Sonnets) than in any given book of the Paradises. And if willful obscurity is what thrills you, there's always Pound.