I get roughly 50% more book space per shelf by using the Lagerfeld Stack™. Browsability is a nice benefit, too. You may want to consider converting to the Lagerfeld Stack™, depending on the dimensions of your shelves. https://twitter.com/wheatpond/status/951570494347710469 …
Perhaps, if you make a memory palace in which to catalogue your ebooks. Then you can indulge in as much shelfy extravagance as your heart desires.