The only book I have ever read more than once is Flowers for Algernon.
I don’t read many books, and when I do, I prefer to read new ones rather than ones I’ve already read before.
Are we related? 
I’ll add James Michener’s The Source. I reread it, at least the first half, about once a year. I’ve read The Talisman a dozen times and I’m now (slowly) making my way thru the audiobook with my husband.
That’s funny. Maybe cold germs last longer than we think…
This, too.
Almost anything by Tamora Pierce: these are my comfort reads.
The exception to this is the Trickster’s Choice/Trickster’s Queen duo. I still think they’re great, but unlike, say, the Protector of the Small quartet they’re not the same level of comfort read for me.
Also, A Tree Grows in Brooklyn.
I’m sure there are more, but these are the ones I turn to over and over.
As a child & teen:
The Little House series
Anne of Green Gables & its sequels
Everything Agatha Christie
Gone with the Wind
As an adult:
The Hobbit and the Lord of the Rings trilogy
All Jane Austen except Northanger Abbey
Pratchett
Lindsey Davis’ Marcus Didius Falco series
Harry Potter series
I also love to re-read anything & everything I enjoyed as a kid, especially when I’m sad.
The Godfather
The Princess Bride
I would estimate I read both titles at least once every couple of years.