People here look at the functional benefit of e-readers without realizing the intangible benefit of paper books. It has nothing to do with the books themselves. The fact that you're reading a book is mostly a mild diversion to the true purpose of reading a book, which is to get laid. Just like everything involving getting laid, the book is a prop that demonstrates certain things about you and given some of the more common traits among millenials these days the right type of book can set you heads above others. This is a drastic change from the past because things associated with being a nerd or intelligent weren't always as highly prized in the past but such things are now considered in vogue.
To a woman, reading a book gives you a sense of aloofness and makes you appear disarmed and less threatening which is good in a society where we seem to be constantly bombarded with men being predators. The construction style of the book (hardcover vs paperback) is one of the indicators they can use to identify your financial stability. People also know that hard covers take more space so if you do keep multiple books and prefer hardcover, a fact you should bring up, it's going to indicate taht you have the space to own and keep multiple hardcover copies, again another financial indicator. The type of book (nonfiction vs fiction) can further reinforce the security of your character. Reading a hardcover of Song of Fire and Ice isn't as good as reading a hardcover version of War and Peace but reading a paperback copy of War and Peace, if that even exists, is still better than reading a hardcover of Song of Fire and Ice. Reading a non-fiction book that is current politcal topic is usually a bad idea. You're going to alienate some women if their political views diverge from the book regardless of your personal views. So I would recommend avoid taking any books on a political figure that has been actived since about 1980. Most of the political figures from before 1980 aren't significant enough factors that ostracize millenials. I'm sure these other advantages that I'm missing but those are just the more obvious signs that can be picked up from books.
e-Readers provide none of these benefits. At best you might get the financially stable bit because you purchased the device but the ebooks themselves are equivalent to paperback in the monetary value of hardcovers is simply not present. Though I really just look at how many women have ended up in my arms because of hard cover books and e-readers and I can say that based on my experience the hard cover book is vastly superior.