I'm the exact opposite: I prefer paper books for 'binge reading', but eBooks for documentation or sifting through, since I'd take Ctrl+F over leafing through an index/glossary any day.

Which is why I think this (and similar offerings: I know O'Reilly and leanpub do similar things) is such an exciting offer: I don't have to sit back and decide which use case I'd rather prioritize.