I think I promised a while back to talk about this, and now I've been asked twice about mine, so here we go. I have this thing called a Bookmate. It has pockets, so you slide the back cover into one of the pockets and then strap your book in. The Bookmate is designed so that it folds up around your book for travel, and then when you are ready to read it sproings open and lays flat. The clear strap lays across the pages, holding the book open so that you can read. When you need to turn the page you fold the book up partially, flip the page, and then pop it back flat.
I use it so that I can read while holding on to the bar on the bus. Or read and knit. Or read and eat. Sure, I can read with the book balanced in one hand, too. But this is a little easier. And I can put the book down without losing my place (or trying to find something to balance it on. It also has a bookmark attached, which is so far the only bookmark I have never lost.
It doesn't break the spine in most cases - I had one book that it did, but likely that book had a wimpy spine.
I got the regular one first. Loved it. Now I have the larger one that fits trade size paperbacks. I gave one to a friend so she could read while nursing. I just love mine. I don't use it every single time I read, but I use it more often than I don't. Great investment. It's also acts as a book cover, so if you want to be discrete about what you are reading - whether because it is a racy cover or a political one, it helps with that too. Without making you look ten years old.