Have you ever found yourself not picking up the book because of being terrified of its size? I have. And I want it to change. From now on, I would dare myself to read 2-3 giant books a year and make it a challenge. It is always fun to tick off a prompt. 
I would consider books to be "giant" when they have 600+ pages. It is up to you to figure out your target page limits.
This is the 2024 challenge edition! See you next year!