I think there is something in this. I used to read paper books prolifically, but through change in lifestyle (kids, work pressures) didn't get round to it so much. The kindle has allowed me to read more again because I can take it everywhere with me. But I certainly get much more confused about which book was which and have less association with who the author was as the whole book purchase decision making is so much quicker.
This means I lose track of which books in a particular series I've read, and find myself wondering if I've read a particular title or not
BUT, I am reading more again and enjoying it when I do. So does it really matter?