I've been swept up in the craze for extremely long lists and compiled this especially for those still in lock-down. To maximise the list's length, I have fused many of my previous challenges, including those below, but also added many extra books.
* Goodreads Highest Rating Books (200,000 to 1,000,000+) - all used
* Goodreads Books With 150,000 to 199,999 Ratings - all used (supplemented by most books 125,000+)
* 237 Books at Least 50,000 List Challengers Have Read - all used
* The Top 500 from thegreatestbooks.org - all used
* All challenges in "The Chronology of American Literature in the 20th Century" series - most popular books used
* Librarything's Top 1000 Books: 001-500 - all used
Alphabetical by title (more or less).
(An ancillary purpose for this challenge is to create a library of attractive, easily accessible icons for compiling challenges. Hopefully with spelling mistakes removed. A dozen or so repetitions were intentional, and a similar number were not.)