It might be a poor example, but David Walliams's book "Grandpa's Great Escape" sold over half a million copies in 2015. The Top 15 of 2015 was (out of interest):
1, Grey: Fifty Shades of Grey as Told by Christian, EL James, 1,075,206
2, Grandpa’s Great Escape, David Walliams, ,532,513
3, The Girl on the Train, Paula Hawkins, 477,887
4, Millie Marotta’s Animal Kingdom, Millie Marotta, 409,858
5 Mog’s Christmas Calamity, Judith Kerr, 382,014
6 Elizabeth Is Missing, Emma Healey, 368,786
7, Go Set a Watchman, Harper Lee, 342,146
8, The Miniaturist, Jessie Burton, 320,648
9, Diary of a Wimpy Kid: Old School, Jeff Kinney, 313,640
10, Guinness World Records 2016, Guinness World Records, 309,900
11, Everyday Super Food, Jamie Oliver, 299,202
12, Personal: A Jack Reacher novel, Lee Child, 289,003
13, To Kill a Mockingbird, Harper Lee, 288,566
14, Us, David Nicholls, 284,105
15, Enchanted Forest: An Inky Quest and Colouring Book, Johanna Basford, 275,182