That physical books age and retain pieces of their history is one of my favourite things about them.

I found a used book that was given to someone when he graduated top of his class in the early 1900s. There was an inscription from the principal of his college, signed and with a seal from the college. I stood there gazing at it and couldn't help imagining how he finished reading it, left it here and there in his house and finally, after his time, in the attic of the ancestral home. It was later discovered by his daughter or granddaughter and then when they were cleaning up, sold to a second hand book seller rather than just destroyed.

Contrast that to a PDF which is just as crisp and clean as it was when it was created (and which could, become a format for which we don't have a reader anymore).