The book is about how selling works, but first let me ask you a question. Are you satisfied with your selling skills?
Can you tell how do your selling skills destroy your ventures, your career, and your future? did you knew that 87 percent of failures in any business are linked to a lackage of selling skills? How would you contribute to the world, your family and yourself if you could sell ANYTHING to ANYBODY? ...
that's how science works. scientists observe a natural phenomena in practice, model it, test their models and publish their theory to the paradigm-addicted community. the community will resist it initially but as anomalies grow, they shift their thinking and adopt the new paradigm. and here is the first scientific paradigm on selling. it is the SPIN theory.
the SPIN theory is nothing but a combination of active listening and the old Hurt-and-Rescue principle revisited. Rackham did extensive researches on top salespeople in action, and modeled their behavior in a linear sequence. one that starts with "opening a call" and ends in "obtaining commitment", and goes through the all-important stage of investigation, in which by asking Situation, Problem, Implication and Need-payoff (thus SPIN) question the seller develops customers implied needs into explicit needs and creates value in their mind, and a demonstrating capability stage in which he shows how the product/service meets the customers expressed explicit needs.
Certainly there is more to sales than just asking questions; but Rackham's classic is yet the most reliable source on selling, and one that I recommend every person to read. if nothing, it will turn people into better listeners and that is good.