If you count each book, there are more than 100, because of trilogies, sets, etc. Each of the following books were published separately, so I count them as individual books, even though they are lumped together on the list:
U.S.A = a trilogy.
The Studs Lonigan Triology = same
The Alexandria Quartet = four separate novels.
A Dance to the Music of Time = 12 separate novels, originally published separately, now published in four volumes of three each.
Parade’s End = four novels, originally published separately.
So even though they call it the Top 100 list, there are really 121 books on it.