As much as I'd like to think this is legitimate, unfortunately, it isn't. It looks like someone cribbed it from
Safari, and put it on their own website. I'm not sure we want to be linking to direct copyright-fringing materials like that..
O'Reilly's version is
over here, and if they allowed full reading/redistribution, it would be made clear on their page. They only have sample chapters available there, and only in .pdf format.
I could be wrong, but I'm pretty keen on this whole "web thing".