> I don’t have the same thing for the ebooks I’ve read, and it gives me a weird feeling of amnesia.

This agrees with studies that show that memory retention is better among students when using physical books rather than ebooks. That's because we're embodied. The book is a physical object with physical features. These intelligible physical features create associations (spatial anchoring, sensory engagement) that reinforce memory. You also get a sense of progress as you read. For instance, when I read something, I better remember at what depth certain content is, and given the depth, I know more or less what is in that part of the book. You could think of it in terms of spatial indexing or in terms of data locality.

People think the medium doesn't matter. They think that it's just a matter of encoding. But the medium very much matters, because the senses are involved in memory formation in all sorts of ways. It's also why handwriting leads to better retention of information than typing.