I finished this book up in the mountains of Jammu, at Patnitop, which is one of the highest points till you reach the Kashmir Valley.
It is very complex, and some parts I do not understand, owing largely to cultural differences. It's a book about life, about the communist regime in Czechloslovakia, about Tomas and Teresa's love, about Tomas's infidelities, about Sabina and her life, about Franz and how he lived and died. It makes you think about your own life as well.
If you think you are carrying a burden, life becomes heavy. What about when life is light? The title itself is a beautiful way to show what the book is about.
I think that you should read it for yourself. I am only just beginning to understand it. Kundera is truly a gifted writer.