There are no absolute numbers to rely on when determining how much of a book may be copied. Babson recommends that each reading be evaluated on an individual basis with the four factors of Fair Use. The smaller the portion being considered, the more likely it is that the use will fall under Fair Use.
You may make a copy of the book once it passes into the public domain. See table, When Does a Work Pass into the Public Domain? to determine if the work is in the public domain.