Back in 2012 I wrote a short piece here about the non-customer. It starts with a complaint I'd apparently been sitting on: that we're all told to identify the ideal customer, and we all dutifully segment and profile the same people as our competitors. Then it hands the rest of the argument to Kim and Mauborgne. Go and find the buyers you've excluded, says Blue Ocean Strategy. Escape the crowded market. Cirque du Soleil did it, so can you.

I found it convincing. I had no idea whether it was true.

It took me years and a book by Byron Sharp to work out that the complaint was sound and the remedy I'd been recommending was probably wrong. That's an awkward thing to learn about something with your name on it. It's also why what follows isn't really a reading list. These five books argue with each other, and they argue about the only question that matters: how a brand actually grows.

Godin: go small on purpose

Seth Godin's This Is Marketing makes the case for deliberate smallness. Stop chasing the mass of people who don't care, he says. Find your smallest viable market instead — a group specific enough that you can serve it deeply, earn attention, and eventually earn a recommendation. It's a generous book. It reframes the job as service instead of interruption, and its instincts are humane ones.

If you're building something small or genuinely community-led, it'll do more for you than anything else here.

Sharp: go broad, and be easy to buy

Byron Sharp's How Brands Grow takes that instinct and runs it through decades of purchase data. Sharp and the Ehrenberg-Bass Institute went hunting for empirical regularities, and what came back looks close to the opposite of Godin.

Brands grow mainly by reaching lots of category buyers. Especially the light ones, the occasional ones, the people who barely think about you between purchases. Loyalty turns out to be largely a consequence of brand size instead of a cause of it: bigger brands have more buyers and somewhat more loyal ones. That's the regularity known as double jeopardy, which William McPhee described in 1963 and Andrew Ehrenberg spent much of a career documenting. Sharp didn't discover it. He dragged it in front of practitioners and insisted we act on it.

He also took a hammer to the 80/20 rule while he was there. Your heaviest 20% of buyers don't deliver 80% of sales — across the categories Ehrenberg-Bass examined it's closer to 50%, and the lightest half of your customers still bring in a fifth. Worse for the loyalty crowd, this year's heavy buyers largely won't be next year's. So the job isn't depth with a few. It's being mentally and physically easy to notice and to buy, for a great many.

You can't reconcile Godin and Sharp by being clever about it. One locates growth in the intensity of your relationship with a narrow group. The other locates it in availability across a broad one, and brings the panel data along.

Where Sharp might not reach you

One thing stops me recommending Sharp unreservedly, and it matters most if you run something small.

Those laws were derived overwhelmingly from big brands in repertoire categories — the supermarket stuff, where people buy from a shifting set of options. Strip the market leaders out of the data and the picture changes. Researchers testing this found the smaller the brand, the more dependent it is on its heaviest customers, with the remaining smaller brands averaging a Pareto score near 78%. Which is to say: something close to the 80/20 rule Sharp spent a chapter demolishing.

I don't think that makes him wrong. His argument is about how brands grow, and a small brand living off its heavy buyers is describing its present, not its route out. But it does mean the reader most likely to be handed How Brands Grow as gospel — the SME owner with forty customers and a modest budget — is also the reader for whom Godin may be the more useful book right now. I'm genuinely unsure where the crossover sits, and I've never seen anyone put a number on it.

Mark Ritson has spent years arguing the whole opposition is a false binary and the answer is plainly both, at different stages and for different jobs. He may well be right. I keep resisting it anyway and I can't entirely account for why. Possibly nothing more respectable than having learned it the hard way round myself.

The word "immutable"

Ries and Trout gave us positioning proper in their 1981 book of that name. The 22 Immutable Laws of Marketing is the compressed, quotable version that most people actually read, and its central claim rearranges how you see the discipline: a brand exists in the customer's perception, not in the company's description of itself.

The trouble is the title.

Ries and Trout put their weight on owning a differentiated position, a meaningful reason you're not like the others. Sharp's evidence points somewhere different. What does the work is distinctive brand assets — the colours, logos, sounds and shapes that make you recognisable at a glance — plus sheer availability. Not differentiation in the sense of buyers holding a considered view of how you differ. Cadbury purple does more for Cadbury than any positioning statement ever written for it, and buyers who couldn't tell you what the brand stands for will still spot it from across the aisle.

So read the 22 Laws as an influential account of how marketers have historically thought about category perception. Don't read it as physics. This is an industry that prefers trend-driven thinking to evidence at the best of times, and a book with "immutable" in the title is catnip to it.

Cialdini and Berger, who aren't in the fight

Influence isn't a growth-strategy book at all, which is why it survives the argument intact. Reciprocity, commitment, social proof, authority, liking and scarcity (the six from the 1984 original, with unity added decades later) describe what happens inside someone's head once your message arrives. That mechanism doesn't care how it got there. Whichever growth model you end up believing, Cialdini explains the moment of yes.

Jonah Berger's Contagious does a similar job for word of mouth, turning why things spread into six workable principles. Of everything here it's the one you can act on soonest.

It needs a caveat, though. Word of mouth is a fine multiplier on a brand that's already easy to find and easy to buy. It's a poor replacement for one. Berger tells you how to give people something worth passing on; he never claims to be telling you how to grow. That mistake is ours.

Where I'd start

Read Godin, and read Ries and Trout, to understand the powerful traditional instincts that built modern marketing. Then read Sharp to test those instincts against the evidence. A marketer who's only read one side of this is considerably more dangerous than one who's read both and knows the argument is live. Cialdini and Berger will make you better at the craft whichever way you come down.

And when you hit the contradiction, which you will, somewhere in the first fifty pages of Sharp, try not to settle it too quickly. Fourteen years on from that non-customer piece I still haven't, quite. The arguing has been worth more to me than any of the answers.