Great pastime, but not very deep

The book opens with a scene from the past, where the main characters are introduced and their relationship gets revealed, although very minimal. All the chapters start with a letter that the two main characters wrote to each other over time and the book also ends with letters, which makes it come full-circle. The plot was also great if a bit remaining on surface level, but the characters were really not written well. They did not have any depth whatsoever and whenever they made a choice there seemed to be no real reason or thought behind that, other than driving the plot. The book revolves quite obviously about the relationship between the characters, which in turn means the individual characters barely have any depth and it really shows throughout the book because they can be very easily swayed on what seemed like a done deal just mere pages ago. The storyline is great and so is the writing style and you really glide through the book, but don't expect very deep characters or much psychological reasoning in this book.