Q. What if I want to quote from a regular book and it is not in public domain? Do I need to get permission?
A. It depends on the length and nature of the quote. If it is a short quote that simply expands on or backs up a point you wish to make, you probably don't need to ask permission. But give credit as to the person quoted and the source of the quote. If the quote is more substantial—such as one of the major premises in that author's book—t hen you will want to ask permission.
It is important to maintain a balance concerning quotes. Don't ask for permission when not needed and don't fail to ask when you should. Usually it comes down to using your common sense and asking yourself if you would want to be asked for permission if you were the quoted author.