I'm sure for authors it can be nervewracking to write a 2nd book after your 1st was such an overwhelming success. Khaled Hosseini has nothing to worry about because "A Thousand Splendid Suns" was every bit as good as "The Kite Runner".
My dad recommended this book to me. He said "check it out from the library, you won't be able to put it down because you will want to know what happens next". He was right. I started it and finished it in two days.
"Kite Runner" was from the male perspective and "A Thousand Splendid Suns" is the story of two women showing that the author can write in either voice. I would try to describe the story but it's too intertwined and I don't want to give anything away. The story is set against the backdrop the modern day history of Afghanistan. Let me just say it's a sad story and not a good choice if you cry in public. But I will echo my dad's suggestion and say get it and read it to find out for yourself.