MCfan2, the newer revivals have taken care of the question of why Guinivere would fall for Lancelot, although I don't think that's why they've done it: Arthur is often cast as an older actor, probably after Burton and Harris started the trend by returning years later to the role.
I, too, love the cast album and the original book, but they're apparently nothing like the version that finally made it to the stage. Why, oh why, would they cut that wonderful men's chorus song, "Fie on Goodness," which is nonetheless on the original cast album?
Audrey, the Phantom Phanatic, who nonetheless would rather be Jean Valjean, who knew how to make lemonade out of lemons.