Haven't you people heard of "Fair Use"?
So I could legally copy an entire book if it were only for my personal,private use,etc.
No. Personal use isn't necessarily fair use. Fair use means that the copy cannot substitute for the real thing (e.g. it is only a very small portion of the complete thing - a few pages, or is stripped of detail, etc.)
Most libraries and schools will have a photocopying licence. This permits the school or library, or its users, to make limited copies of the books that they hold, over and above "fair use". Typical licence terms would be something like: a student is permitted to make a single copy of up to 1 chapter of a book, for their own personal use. Most licences will require that the copy be recorded in a log, stating the name of the person for whom the copy is to be made, the name of the book, and which pages have been copied. This is to permit auditing, so that a violation (e.g. you photocopy chapter 1 on Monday, and come back on Tuesday to copy chapter 2) can be detected.
If a book is out of print, you still are not permitted to copy the entire thing, as that would not be fair use - there is a still a copyright holder (albeit they may be difficult to trace and uncooperative) that is entitled to their rights. For highly desirable out-of-print books, the second-hand prices can be astronomical. I've seen a number of very specialist textbooks, now out of print, which go for 10x their new cost - simply because of the clarity of their writing which has yet to be matched by more recent competitors.