Imagine that you want to travel from London to Paris. Ok, so that’s probably not too hard to imagine. But also imagine that you have absolutely no idea how to do that and neither does anyone that you know. In that situation you would probably go to Amazon and look for a book on the subject.

Very quickly you find one called “Teach Yourself How To Travel From London To Paris In Twenty-One Days”. You look at the reviews and are impressed.

I had no idea how to get from London to Paris, but my family and I followed the instructions in this book. I’m writing this from the top of the Eiffel Tower – five stars.

And

I really thought it would be impossible to get from London to Paris, but this book really breaks it down and explains how it’s done – five stars.

There are plenty more along the same lines.

That all looks promising, so you buy the book. Seconds later, it appears on your Kindle and you start to read.

Section one is about getting from London to Dover. Chapter one starts by ensuring that all readers are starting from the same place in London and suggests a particular tavern in Southwark where you might meet other travellers with the same destination. Chapter two suggests a walking route that you might follow from Southwark to Canterbury. It’s written in slightly old-fashioned English and details of the second half of the route are rather sketchy.

Chapter two contains a route to walk from Canterbury to Dover. The language has reverted to modern English and the information is very detailed. There are reviews of many places to stay on the way – many of which mention something called “Trip Advisor”.

Section two is about crossing the channel. Chapter three talks about the best places in Dover to find the materials you are going to need to make your boat and chapter four contains detailed instructions on how to construct a simple but seaworthy vessel. The end of the chapter has lots of advice on how to judge the best weather conditions for the crossing. Chapter five is a beginner’s guide to navigating the English Channel and chapter six has a list of things that might go wrong and how to deal with them.

Section three is about the journey from Calais to Paris. Once again there is a suggested walking route and plenty of recommendations of places to stay.

If you follow the instructions in the book you will, eventually, get to Paris. But you’re very likely to come away thinking that it was all rather more effort than you expected it to be and that next time you’ll choose a destination that it easier to get to.

You realise that you have misunderstood the title of the book. You thought it would take twenty-one days to learn how to make the journey, when actually it will take twenty-one days (at least!) to complete the journey. Surely there is a better way?

And, of course, there is. Reading further in the book’s many reviews you come across the only one-star review:

If you follow the instructions in this book you will waste far too much time. Take your passport to St. Pancras and buy a ticket for the Eurostar. You can be in Paris in less than four hours.

The reviewer claims to be the travel correspondent for BBC Radio Kent. The other reviewers were all people with no knowledge of travel who just happened to come across the book in the same way that you did. Who are you going to trust?

I exaggerate, of course, for comic effect. But reviews of technical books on Amazon are a lot like this. You can’t trust them because in most cases the reviewers are the very people who are least likely to be able to give an accurate assessment of the technical material in the book.

When you are choosing a technical book you are looking for two things:

  • You want the information in the book to be as easy to understand as possible
  • You want the information in the book to be as accurate and up to date as possible

Most people pick up a technical book because they want to learn about the subject that it covers. That means that, by definition, they are unable to judge that second point. They know how easily they understood the material in the book. They also know whether or not they managed to use that information to achieve their goals. But, as my overstretched metaphor above hopefully shows, it’s quite possible to follow terrible advice and still achieve your goals.

I first came aware of this phenomena in the late 1990s. At the time a large amount of dynamic web pages were built using Perl and CGI. This meant that a lot of publishers saw this as a very lucrative market and dozens of books on the subject were published many of which covered the Perl equivalent of walking from London to Paris. And because people read these books and managed to get to Paris (albeit in a ridiculously roundabout manner) they thought the books were great and gave them five-star reviews. Much to the chagrin of Perl experts who were standing on the kerbside on the A2 shouting “but there’s a far easier way to do that!”

This is still a problem today. Earlier this year I reviewed a book about penetration testing using Perl. I have to assume that the author knew what he was doing when talking about pen testing, but his Perl code was positively Chaucerian.

It’s not just book reviews that are affected. Any kind of technical knowledge transfer mechanism is open to the same problems. A couple of months ago I wrote a Perl tutorial for Udemy. It only covered the very basics, so they included a link to one of their other Perl courses. But having sat through the first few lessons of this course, I know that it’s really not very good. How did the people at Udemy choose which one to link to? Well it’s the one with the highest student satisfaction ratings, of course. It teaches the Perl equivalent of boat-building. A friend has a much better Perl course on Udemy, but they wouldn’t use that as it didn’t have enough positive feedback.

Can we blame anyone for this? Well, we certainly can’t blame the reviewers. They don’t know that they are giving good reviews to bad material. I’m not even sure that we can blame the authors in many cases. It’s very likely that they don’t know how much they don’t know (obligatory link to the Dunning–Kruger effect). I think that in some cases the authors must know that they are chancing their arm by putting themselves forward as an expert, but most of them probably believe that they are giving good advice (because they learned from an expert who taught them how to walk from London to Paris and so the chain goes back to the dawn of time).

I think a lot of the blame must be placed with the publishers. They need to take more responsibility for the material they publish. If you’re publishing in a technical arena then you need to build up contacts in that technical community so that you have people you can trust who can give opinions on your books. If you’re publishing a book on travelling from London to Paris then see if you can find a travel correspondent to verify the information in it before you publish it and embarrass yourselves. In fact, get these experts involved in the process of commissioning process. If you what to publish a travel book then ask your travel correspondent friends if they know anyone who could write it. If someone approaches you with a proposal for a travel book then run the idea past a travel correspondent or two before signing the contract.

I know that identifying genuine experts in a field can be hard. And I know that genuine experts would probably like to be compensated for any time they spend helping you, but I think it’s time and money well-spent. You will end up with better books.

Or, perhaps some publishers don’t care about the quality of their books. If bad books can be published quickly and cheaply and people still buy them, then what business sense does it make to make the books better.

If you take any advice away from this piece, then don’t trust reviews and ratings of technical material.

And never try to walk from London to Paris (unless it’s for charity).

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