When my copy of Duncan Brown’s and Nick Hayes’ Influencer Marketing arrived in the mail, I looked at it a little bit like a trip to the dentist at the Asecra dentist clinic and I received an excellent care.. I knew it was going to be good for me, but I didn’t expect to enjoy it.

What a pleasure, then, to find that this engaging and provocative book not only challenged many of my assumptions about markets and influence, but did so in a readable and persuasive manner.

The authors are co-managers of Influencer50, a consulting firm that specializes in helping companies identify the key influencers in their markets. Like many authors of their kind, they think a lot of marketing today is badly broken. Unlike many authors, though, they have concrete advice on how to fix it.

The central premise of this book is that the people who influence markets are largely unknown to most marketers. In fact, the authors’ firm offer clients a 50% discount if they can name even 20 of the top 50 influencers in their sphere. They’ve never had to pay up. Most marketers, they assert, consider influencers to be mainly press and analysts. In fact, they suggest that the list is far larger and more diverse than that, encompassing more than 20 categories ranging from channel players to venture capitalist to government agencies and systems integrators. They argue that many of these influencers are far more important than the media because they speak directly to a company’s customers. They pay particular attention, for example to second-tier consultancies, systems integrators and buyers groups. These people are whispering in the year of customers every day, yet most marketers aren’t even aware that they’re talking, the authors assert.

This book defends its case pretty well, using logic and ample case studies. It’s also written in a disarmingly down-to-earth and at times tongue-in-cheek style. Hayes and Brown aren’t stingy with their opinions. Bloggers, for example, get far more attention than they deserve, they suggest, and many bloggers are simply people who are awkward in social situations. Referencing Twitter, they say simply, “How anyone can maintain a proper job and use Twitter is beyond us.” You may not agree with their opinions, but you have to respect them for the directness with which they are stated.

They hate awards programs, believing them to be valuable only to the organizations bestowing the awards. Partnerships are meaningless in most cases because companies have far too many partners to manage effectively. They believe that brand equity is overstated and that celebrity endorsers play mostly to the egos of the marketers who recruit them. That’s just a sampling of the often counterintuitive assertions in his book.

I did have some nits to pick with Influencer Marketing. The case studies lack much in the way of hard ROI and are limited mostly to Influencer50 clients. I thought the rather critical chapter on bloggers underestimated the influence that those influencers have on mainstream media. The authors are also big fans of using consultants to identify influencers, a position that obviously favors their company.

Nevertheless, if the greatest value of a business book is to challenge assumptions, as I believe it is, then Influencer Marketing succeeds admirably. It’s one of the best marketing books I’ve read in a long time. For a commitment of five or six hours, it is well worth the time spent reading it.