Depends on what kind of books you like to read. What is a series you have read before that you really liked and wasn't too mentally challenging to read?

I think one of the things that makes my "comfort reads" comforting is that I have already read them before, so I already know I like them. But also they are long or a series, so I have forgotten some details that I get to rediscover. And it just blocks out a decent chunk of my future reading time so I stop trying to organize my line up of next books to read.