It would be illegal to obtain the entire copy without paying for it. The reason that several chapters are on their website, is because they own the copyright or have a legal written agreement with the copyright holder and can do what they want with it. If they want to post the whole book for free, they can (again, because they own the copyright or have a legal written agreement with the copyright holder and can do what they want with it.). Unless expressed, it would be safe to assume that you cannot take those snippets and post them on your own website.
Nobody else can. When you 'buy' it, you are not 'buying it'. You are buying the rights to view it. You do not own it.
Same with video games, CDs, paperbooks, and DVDs. When you buy one, you don't own the movie, or game, or book, or CD. You own the right to watch the movie/play the game and they provide a copy of it for your own use.
I remember a while back that major game companies tried suing companies like Gamestop for resaling games. Even farther back, I remember movie companies wanting to charge for movies being played in classrooms. If you look at the back of a game box or dvd, it probably says that you cannot copy it, resale it, rent it, charge people to play it, etc. Companies that you rent games and movies from, have paid a hefty price for the rights to do so. They don't just go to the store, buy 10 movies, then rent them out.
I'm no lawyer, but for common people, it is probably safe to assume that unless you paid for something and bought it from the original owner (or a company that is credited for being trustworthy), you don't have the right to use it.
Work smarter. Not harder. I think.
