Book 4 really took the wind out of my sails, that's the one where Aneas leaves Dido. I pushed through to Book 6, that's the one where Aneas goes to the underworld. I felt that 6 was a let down. The last 6 books are less remarkable with the Trojans fighting the natives.  I read this in college and know how it goes. I had a big head of steam but petered out.