Originally published at the end of the Eighties, SPIN Selling details a questioning technique that prompts prospects to identify and explore the severity of business problems, and then understand how your solution would resolve their issues.
In contrast to the aggressive and combatitive approaches before it, SPIN Selling turned the sales call into a constructive experience for the prospect and greatly lowered the number of objections received by sales people. It was so effective that it became widely recognised as the Grandfather of all modern sales techniques.
This book can genuinely claim to be a classic sales text, though it is fair to say that newer methodologies, based on SPIN, have been developed that augment and extend the core of the SPIN model. For example, some newer methodologies offer an end-to-end guide to selling (e.g. how to generate and manage opportunities, understanding the prospect company structure, precall planning, predicting successful close probability, etc), all of which are extremely useful, but absent in "SPIN Selling". Furthermore, the business environment has change significantly since the publication of this book and therefore, some of the techniques suggested in this title require "tweaking" in order to be useful today.
If you are already familiar with consultative/solution selling techniques, then you will find little helpful content in "SPIN Selling" (as what you have already read/been trained in, will probably have stemmed from SPIN in the first place!) If you do not currently employ a question-based, problem solving approach to selling, then this book will unquestionably up your sales. However, a title like "New Solution Selling" (by Keith M Eades) would provide you with a similar approach that is better suited to the temperament of today's buyers, plus you would benefit significantly from a more complete methodology to guide your sales activities.