What was lost

The premise sounds interesting: a new version of Harriet the Spy, but written for adults. But the book fell completely flat. It took the writer ages to develop the main character (a young girl intent on starting her own investigation agency) only to completely uproot the reader halfway through with a handful of underdeveloped characters struggling to find out about said little girl. If the author was going to take so much time to tell us the entire history and inner workings of the main character, why waste it all on abruptly ending her narrative? Maybe it was to demonstrate how you in life you grow to understand someone, slowly learn their background and quirks, only to have the person disappear from your life for one reason or the other. And then their story is over for you. Still, it felt like a waste of time. The story telling was so detailed to reach the point where you could understand the girl... It isn't that it's a bad story, or that the writing style wasn't good. It didn't feel like it had been planned out well, or that maybe she had planned for it to be a longer book but ran out of ideas.