That is the question that is being answered on the Unashamed Workman Blog. I would encourage all preachers to go on over and look at this 6 part series that looks at 6 Biblical images of the preacher. The first 3 have already been posted. The Hard Working Farmer, The Law Abiding Athlete, and the Good Soldier.
If you want to see what Christianity Today thinks are the top 50 books that have shaped the evangelical movement then look here.
The Purgatorio blog has given 50 more books that didn’t make the list, but should be considered…You can see that list here.