I highlight often when reading on my kindle. I have created a small program that scrapes my highlights and sends me a daily email with one of them. I get it before I wake up and it’s the first thing I read once I check my email (usually that happens after my morning reading).

I find that this helps remember books that I read years ago, and usually the single quote is enough to jolt a series of memories about the book.

That said, I also own physical books and they are in glass bookshelves around my office and living room. I do like the looks of them and they can be a conversation starter as well when friends come over.

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

I have a similar feeling when it comes to my music collection, some of which includes rare recordings. I ripped everything and have it at my fingertips on my phone, computer, etc, but I often find that I’ve forgotten when I have. When I was younger, I kept it all on a shelf. Browsing one’s music collection (or a friend’s) was always a pleasant way to spend an evening socializing. With apps, that is all gone. I have recurring fantasies about building some kind of physical music player, with cartridges that one could insert into a “player”. The actual music would be stored centrally, but this would be more like a mnemonic device to make browsing more enjoyable. I could imagine a similar thing for ebooks.

I'm not an ebook reader, but I would have assumed that these apps would have some sort of indication if you've read a book or not and if you've not read to the end some sort of progress. Like opening an ebook that you did not complete should hopefully take you to where you left off at a minimum. I'd also expect your app to have a management type of display where I'd expect some sort of sorting/filtering where you can see only the books completely read, the books started but not finished, and books not yet started. I'd even somewhat expect a skeuomorphic layout of books on a shelf that you could somehow rearrange like it was iPhone 1.0. Again, I'm not an ebook person and never used any of the apps, so maybe these are standard things. However, it should make things easier to know if you've read them or not.

I have mixed feelings about Kindle, but I mostly read books on my phone these days, and my Kindle library is always there. I also have a physical bookshelf, but if I'm not home I can't review it so in some ways it's often less tangible than my Kindle library which I always carry with me.

> 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.

Have you considered printing a book side and putting it on a wall as a growing poster while keeping a Calibre or Zotero collection in sync?

I share this feeling. When I want to free up some space, the books I get rid of are the ones I don't remember reading.