I love paper books. But I can't store them, not when there are six people in my house,and five of them are hardcore readers. We have at least one bookshelf in every room of the house (including the bathroom and the kitchen); I have three just in my bedroom, and they're all seriously overflowing. I have boxes of books stashed under all the beds in the house, under the sewing table, on top of my piano, in the barn loft out back, etc.
I HAD to go to electronic books as soon as the prices became low enough to be viable for me (and I ended up buying like six ebook readers, to share out with the family), because otherwise the house would be one big bookroom, and I'd be sleeping in a tent in the front yard.
With that said, I do have books that I will buy both an e-copy and a hard copy. The e-copy to read, the hard copy because I want to preserve it.
Confession time: every time a new Dresden Files comes out, I buy FOUR copies: one hardback, one paperback, one e-copy and the audiobook. The hardback is for preserving, the paperback is for loaning out (infection vector), the e-copy is for reading, and the audio is for my husband to listen to when he's on the road.
As for going to the library: it's a forty minute drive, one way, for me to go to the library, which, with the cost of gas nowadays, means it actually would cost me less to buy a book online than to go to the library. And even if I made the trip, their selection is crap.