Mourning Ruby by Helen Dunmore
The main story thread in this book is about Rebecca, who was found in a shoebox, finally creating a family for herself by marrying and having a baby, Ruby. However, she loses her daughter in an accident, and her relationship with her husband fails as a consequence. Her friend, with whom she lived for a long time, but whose relationship never developed beyond the platonic, has been trying to write a history book about Stalin, but gives it up to create a new fictional story of Rebecca's unknown family in an attempt to help her. The final part of the book consists of parts of this story, set in the First World War, and seems to be a rather unimpressive attempt to emulate Sebastian Faulkes. However, the present-day elements were captivating, especially (for me) the Moscow-based section which seemed very accurate.