Sashenka by Simon Montefiore
If you are looking for a book to tide you through the last chill of winter, this is it. The author is a very well respected historian, so you know that what you are reading is grounded in horribly accurate research. In fact, as he says in the afterword, although the events described may seem extraordinary, the reality is that Sashenka's story was really quite commonplace in Stalin's Russia.
I finished reading it while stuck in snow at Newcastle airport. It's amazing how getting back from holiday at 4am really wasn't such a drama after all as I sat in my nice cozy aeroplane tearing through to the end, but still not sure I wanted to find out what happened.