Kieran Healey at Crooked Timber reviews a biography of Darwin which seems like a very worthwhile read. It rings true to me, in my own attempts to glimpse into the cloud of unknowing, that an alternation between very good scientific correspondence and moments without distractions (..uh, like blogging?) is a very healthy routine for thinking.
Read through the comments for some thoughts on the crisis Darwin provoked among Victorian believers. I think it may be a mistake to pin all of this on Darwin; a careful read of Voltaire can scald the retinas.