This is the paperback release of 'A Dance with Dragons' - and has been split into two separate books for two reasons: 1 - Length. The book is huge, so it has been broken into two books like A Storm of Swords was. 2 - A Feast for Crows and A Dance with Dragons both take place at the same time (for the most part). Once it reaches the chapter 'The Turncoat', the books have synced up. So, the split also marks the point where the two books meet - basically, Part 1 entirely happens at the same time as A Feast for Crows, whilst Part 2 is what happens next.