I loved this book when I was a teenager, I still like it fondly now. It's part of a trilogy - but don't bother with the third book, it's rubbish. In fact, don't bother with the second book either - though it isn't bad.
The love story between Tatiana and Alexander is heart wrenching and beautiful - the characters are well drawn out. I have nothing but admiration for Tatiana, although she's a little too nice and perfect.