The value of a Smart Questions book is not from book sales, but the influence and credibility it gives.
For an employee
A book can build personal brand, increasing your promotion. What better way to say "I really know my stuff". Picked carefully the reviewers could open up potential new jobs. If you are currently between jobs, a book could get you that next position.
For an independent consultant
It can raise your profile, and increase consulting day rate, and drive business development. Just saying "I'm an author" really changes your credibility. A book is far more valuable marketing material than any brochure or website, and can be cheaper too.
For a company
For a company, a book can raise awareness or educate customers about a new approach or product - provided it is valuable and has 3rd party credibility. Used carefully it can change client expectations and in cometitive situations 'move the goalposts'. It can be far more cost-effectively than a traditional PR or marketing campaign.
Cheaper than brochures for promoting you or your company
A limited volume print run can be cheaper that the cost of developing and printing a brochure. Yet a book is kept by potential customers long after your marketing brochure has hit the trash.
"I can point at over £2million of sales that came directly from my first book. My only regret is it cost us over £60,000 to get it published"
Ian Gotts, author of Common Approach, Uncommon Results