I found the best part of the book to be the initial story-foundation phase where the author describes the setting (pastoral NW France of the mid 19th century -- very pretty, think pastels and ripe rolling grain fields and small farming towns with few houses and fewer roads) upbringing, and influences. He names literary works that had an influence on each character. These works are easily found on Wikipedia and are very interesting leads for further historical reading.
As for the story: somewhat frustrating. How do you deal with a person with a "grass is always greener" complex. Madame Bovary could have had a pretty good life as the wife of a country doctor. But she threw happiness away with both hands grasping after some fleeting happiness or other that never really brought satisfaction, and usually brought more debt. I was actually hoping that she would go whole-hog with the adultery thing, go to Paris and open a house of ill-repute. Take the town by storm. Anything. But no. Always half-hearted attempts without knowing herself or her real goal. Tiring.
Of course the wikipedia entry on Bovary explains the author's intent much better than you can get out of the book. It's basically a critique of the new French bourgeois. She is middle class and attempts to climb, but the very middle class she tries to climb out of pulls her down. She dies, he dies, everybody dies, and her neglected daughter ends up in a textile mill (tough work). The end. Thanks, Flaubert.