Recently I've been re-reading some old books recently, which I bought a few years ago. Recently I've been re-reading some old books I bought a few years ago.

It seems a little lazy because I already know about these books, but it's cozy for me to reread them. It seems a little lazy because I already know about these books, but it's cozy for me to reread them.

"but I feel cozy rereading them" sounds a bit better

It seems a little lazy because I already know about these books, but it's cozy for me to reread them. It seems a little lazy because I already know these books, but it's cozy for me to reread them.

"know about these books" suggests you know of them but haven't read them. Saying you "know these books" feels more natural

It seems a little lazy because I already know about these books, but it's cozy for me to reread them. It seems a little lazy because I already know about these books, but it's cozy for me to reread them.

It seems a little lazy to read the same books again, but it feels cozy when I re-read them.

It seems a little lazy because I already know about these books, but it's cozy for me to reread them. It seems a little lazy because I already know these books, but it's cozy for me to reread them.

"to know about" is to be aware of. "to know" is to understand or be familiar with. Your second sentance is a little strange sounding, perhaps reword or change "cozy" with "comforting" or "nostalgic"

Sometimes I find some new points I've missed before, and sometimes I just read one of the books before falling asleep. Sometimes I find some new points I missed before, and sometimes I just read one of the books before falling asleep.

Sometimes I find some new points I've missed before, and sometimes I just read one of the books before falling asleep. Sometimes I find some new points I missed before, and sometimes I just read one of the books before falling asleep.