The last one hundred pages on this two-work volume are in fact the earlier work, "Scientific Advertising", written in 1923, while the first 210 pages represent Hopkins' auto-biography, published in 1927, five years before his death in 1932. On reflection, I would have read the volumes in their chronological order, as Hopkins had covered many of the examples he used in his earlier work more fully in his memoir.
This book is an interesting historical resource - I remember that my mother had a Bissels carpet sweeper, and it is therefore interesting to discover how Hopkins helped them achieve market domination through the development of a USP which, interestingly, had nothing to do with the machines' technology. We also learn of Hopkins' involvement with other brands that are still well known today - Palmolive, Goodyear Tyres and Quaker Oats - while it is also interesting to realise how many of the great brands of the 1880s to 1920s have now vanished.
Hopkins wrote the book as a guide to others, and opinions will differ as to whether what he says about advertising is still relevant. Hopkins repeats the importance of testing advertising effectiveness, tracing the cost of acquiring a customer, the value of subsequent sales and the lifetime value of a customer. He believed in testing on a small scale first, and demonstrated that sales statistics calculated on those small scale tests would be repeated later in larger, often national, campaigns. He emphasises that it is the headline of an advertisement that gets attention and makes the difference, having tested many adverts with the same content but different headlines and tracked different response rates. He believed in telling the story about a product and using personal stories about key people in businesses. Ads, he said, should be "salesmanship in print", a term he picked up while working at the Thomas & Lord agency. He advocated offering free samples, but that these should not be distributed "promiscuously" but should be available for collection, on delivery of a coupon, through the normal retail outlets. He used guarantees to reassure potential customers, but wrote them in commercially cautious ways.
Much subsequent marketing theory is here in nascent form - Hopkins doesn't use the terms USP, market segmentation or targeting for example, but the ideas are all here. While Hopkins uses the term advertising, his techniques went well beyond the tight definition of advertising into other marketing methods - direct mail, point of sale support for retailers and other techniques. This book is not narrowly focussed, and that is why I believe that it stands the test of time. Hopkins used the media that were available to him at the time, but the principles that he applied are largely applicable with the other media now available, including all of the various online promotional channels. Indeed, he would have been excited by the many new ways of tracking advertising effectiveness that new technology has made possible, while being astonished how much advertising effectiveness is still not measured.
What is missing, and what would make a great research project, would be to find examples of the actual adverts, sales letters and pamphlets that Hopkins wrote, and if possible also to find the data that he compile to measure their effectiveness. In fact - it's probably been done - if anyone knows of such papers do please point me in the right direction.
These books are both easy to read, and I agree with David Ogilvy: " nobody should be allowed to have anything to do with advertising until he has read this book seven time". I'd go further: I think that you can safely substitute the newer work "marketing" for the older "advertising".