...or just gave up on. You got stuck, and couldn't proceed further, or you just felt you'd read enough. You have plans to return to them one day, and complete the deed; or not. Off the top of my head:

Doris Lessing - Shikasta
John Updike - Couples
Thomas Pynchon - Gravity's Rainbow
Mikhail Bulgakov - The Master and Margarita
Yu Hua - Brothers
Margaret Atwood - The Edible Woman