Well if the cost of photocopying the book would be lesser than, let's day searching the web for a cheaper used copy of the book then I'd say yes. But for the most, not unless the book was super rare that you can't find any used copies being sold for $5 on eBay or Amazon then I could make the effort.
No, I would not copy an entire book from the library. I have copied a page or two here or there, usually from cookbooks or craft resources. However, if I find a cookbook that I really enjoy and would uses many of the recipes over and over again, I purchase it. Even if I have access to a copy machine and wouldn't have to worry about the cost of the copies, the time it would take to copy is consuming. In addition, I would have to find someway to store the copy of the book (probably in a binder). By the time you add up the time it takes to copy and put together the copy of the book, the alternative of buying the book becomes much more appealing.
No way! It's just too ugly for me. I have to deal with enough photocopies at school, and they're bad enough. I don't really know why someone would want to do that, but I guess if it's just a page or two it wouldn't be too bad. I'm pretty sure it's legal to do that anyways, as long as you don't plan on photocopying a large chunk of the book (or the entire thing) you should be perfectly fine. Please, just buy it...
Yes, if the book is extremely expensive and that I wouldn't be really needing the whole of it, just parts. And also, if the book isn't really that I would die without reading it. If it were really not the book of my type, just a book required to be read in the class, for example. I would rather photocopy than buy it. Sure: it's going to save me quite a good sum of money. Besides, books now often come with a pdf, that if I need it to see in particular details that colors will greatly matter, I could always consult that soft-copy version of the book. I also think that pdf versions are far cheaper than the exact book itself.