[uticus]

The benefit for me has been the ability to skim books. I'd love to learn there was an alternative way to skim or form an opinion about a book, before buying.

Normally I would treat buying nonfiction as something worthwhile. But buying a book related to software is often a great way to purchase something irrelevant six months later. O'Reilly enables me to check out new stuff, form opinions about the keepers, and read about the latest stuff that I know will be replaced very soon but is in hot demand right now.