The great thing about libraries, blockbusters and stores is that you can peruse and find things that you didn't know you wanted. When you're looking through the call numbers for your book you'll see plenty of related and unrelated material depending upon how the place is laid out. Sure to some extent internet places have got this with showing other items in the sidebars but that's not quite the same: if you wanted a hose in a hardware store you'd (potentially) walk through unrelated departments and see tons of items that might catch your interest but were in no way related to what you were looking for. and even when you got to the hose section there'd be a variety of hoses and hose related materials that you didn't even know existed. online shopping is usually "specific search term" sorted by lowest price.