Determine the valence intensity of the following tweet, considering the mental state of the author. Assign a real number between 0 and 1, where 0 denotes extremely negative and 1 denotes extremely positive.
Tweet: @xiankiefer @TheLincoln Book 5! It's so sprightly &amp; fun cuz he'd been reinvigorated by the Harry Potter series. I'm not kidding.
0.781