Books that can help don't necessarily have to be on social engineering. Check out books on communication, corporate psychology, basic psychology, and selling skills.
These will help you be a better and more persuasive person overall and understand more about what your "mark" is thinking by how they respond.
A good book on reading body language, communication, negotiating, assertiveness, public speaking, active listening, and transactional analysis is MESSAGES: The Communication Skills Book.
That would be a pretty good start in learning the basics, because all those skills are important in life, work, and social engineering.
