These are books that scored at least 200,000 ratings from the users of Goodreads, as at 24 January, 2020. So if you like to discuss books with others that have also read them, this is the list for you.
They are broken down as follows:
01-76: 1,000,000 or more ratings
77-210: 500,000 to 999,999
211-625: 200,000 to 499,999
Some books were duplicated on the 3 Goodreads source lists I used, but I aimed to make this an exact replica of those lists, so the duplicates have been retained. Similarly, individual books in series appear in the challenge if they met the popularity criterion as listed above.