WIIFM is what motivates a person to buy something.
I may purchase Dr. Pepper Ten over regular Dr. Pepper because the Ten one tells me that it only delivers 10 calories per serving, allowing me to cut down on my calorie intake. I may purchase Colgate Luminous toothpaste even though it costs me more than other toothpastes because it promises to not only whiten my teeth, but also strengthen my enamel.
As humans, we are motivated to buy something for what we can get out of the thing we are buying.
WIIFM is the most important question every publisher and author must answer for their potential readers. What does your book contain that the reader will benefit from? In other words: What will the reader get out of reading your book?
When creating your sales pitch and all your marketing materials for your next book, answer this question for your potential readers. All your sales text— back cover copy, marketing materials, book descriptions, etc.—should answer the WIIFM question.
Tell your potential readers what they will get from your book. Tell them how your book will improve their life or meet a need they have. It’s that simple.
What’s in it for you? Answer: More book sales!