Here are the top ten titles, by circulation, of middle-grade fiction this year:

10. Dork Diaries: How to Dork Your Diary by Rachel Renée Russell

9. Wonder by R. J. Palacio

8. Diary of a Wimpy Kid: Double Down by Jeff Kinney

7. Diary of a Wimpy Kid: The Last Straw by Jeff Kinney

6. Diary of a Wimpy Kid: Cabin Fever by Jeff Kinney

5. Diary of a Wimpy Kid: The Ugly Truth by Jeff Kinney

4. Harry Potter and the Sorcerer’s Stone by J. K. Rowling

3. Diary of a Wimpy Kid: Greg Heffley’s Journal by Jeff Kinney

2. Diary of a Wimpy Kid: Dog Days by Jeff Kinney

and … here it is … the winner for 2017:

1. Diary of a Wimpy Kid: Hard Luck by Jeff Kinney

It’s obvious: there’s a theme here.