"Fair use" is the doctrine that allows for small portions of a work to be used in total without permission.
"...fair use of a copyrighted work, including such use by reproduction in copies or phonorecords or by any other means specified by that section, for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is not an infringement of copyright. In determining whether the use made of a work in any particular case is a fair use the factors to be considered shall include—
As a general rule of thumb, one chapter or less than 10 % of a work is usually considered a fair amount.