By the Wrath of God, Queen of England, by Alison Weir.
Quickie recap: Eleanor's beauty and her inherited wealth apparently made her a desirable woman and a desirable wife - when she demanded an annulment from her first husband (king of France), she quickly found another (who would become king of England) despite the fact that she had not proved she could provide male heirs.
Quickie review: Eleanor actually seems like an interesting historical figure, but you'd never know it after reading this book. It was so dry I had to read it while floating in the pool just so I wouldn't spontaneously combust.
Quickie recommendation: Skip it - a real snooze-fest.