I still laugh about the chapter in the middle of Les Miserables where the author spends something like 20-30 pages talking about the battle of Waterloo. It was interesting, and very detailed, but had nearly no connection to the plot of the story (other that one of the people there left an heirloom for a character, or something?). Later, he did the same thing for the sewers of Paris, and I believe I skipped that. ;)