I'm a bit of a bookworm, so there's my bias. But... reading a book is almost certainly a better use of time than, say, farting around on Imgur, or looking at celebrity gossip web sites, or playing Minecraft.
Is it better than, say, learning differential equations on a MOOC web site? Probably not. I expect the number of people "wasting time" on the Internet far exceeds the number learning DiffEq, though.
