Gone are the days of lugging travel books around the globe. Today you can leverage your digital gizmos and download all your travel books onto your device of choice: Kindle, iPhone, iPad, Galaxy.
Lonely Planet, Frommers, Rick Steves are all available in electronic form from Amazon and others (Nook, Apple Books, etc) and slightly cheaper than the cellulose-based tomes.
They are also, of course, much lighter, but they are not light on content which appear to be equivalent. See the comparison (at right) of the written page versus the e-book equivalent. Obviously the e-book can take advantage of links to hop around in the book. So the benefit is really weight, some cost, and portability.
I agree that a paper book can be nice to flip through, but for space and weight, which would you rather carry? Here are the same books in digital form all in the comfort of my iPhone.
Happy RTW Travels!