A book is like a map. It describes a certain terrain. Even fictional books may describe a real-world terrain, sometimes unwittingly, but I mainly have non-fiction in mind, and metaphorical maps.
When I consult a map, there is a vital piece of information I must obtain, before the map will be useful to me. It is the first thing that Google Maps puts on the screen, even before it's downloaded the map data. It's the blue dot: where am I? Until I know where I am on the map, I cannot use the map to find my way.
The GPS hardware on the phone tells Google Maps where I am. But there is no GPS for the mind. When I pick up a book, it is up to me to find where I am on the author's map by looking for some part of it that matches terrain that I know.
Every book or teaching is addressed to an imaginary person in the author's head, some idea of where "most people" are, or "the sort of people" he wants to reach. But there is no such person as "most people". It is as if Google Maps, seeing that I am in London, were to display not my location, but the average location of everyone in London. I could do nothing with that. "Where most people are" is not the location of any individual. What matters to me when examining a book is, where am I on this map? When I know that, I can make use of the book.
When the book is on a subject that deals with the external world, whether that be mathematics, history, or woodworking, I can easily tell where I am on the map. A textbook might be too advanced, and I must first learn some prerequisites, which the author may have specified. Or it might be too elementary, and I may only skim through it as a refresher, or pass it over. Or it may be about an aspect of the subject that I am not concerned to learn. Eventually I will find a map that shows me both where I am, and the territory I want to explore.
When it is about psychological or spiritual matters, then I can never be sure that when trying to find myself on the map the author has drawn, I am not trying to find my way through Berlin with a map of London, or a map of Mars, or a map of an imaginary place the author has dreamt up. I cannot see your mind and you cannot show it to me; you cannot see my mind and I cannot show it to you. On such matters there is nothing outside us that we can both point at, and agree on what we are pointing at. The words anyone uses point to where nobody but they can see. I am not the only one who suspects that every grand psychological theory is better understood as a map of its creator's mind than any sort of universal truth: the typical mind fallacy writ large. Even if the map is of somewhere on the same planet as myself, I still must find myself on it before I can use it to go to the places on the map.
Often, the author puts a big "You Are Here" sign on the map. I have noticed that nearly all self-help books, from the tritest offerings in the Mind, Body and Spirit section of the local bookstore to the loftiest of teachings, begin by telling the reader what a schmuck he is. (What, even after they've studied your book and practiced what you preach?) That's their "You Are Here" sign. It is as if a guidebook for pilgrims to Santiago de Compostela were to insist that everyone starts out in Paris. Maybe I live in Genoa and have no reason to go near Paris. Maybe I am already in Roncevalles and the author himself has never been so far. But no, the author insists you're in Paris, and anything you might say to the contrary is evidence that you're in Paris, and the first thing you have to do is to accept that you're in Paris. Only then can you get out of Paris. This is especially true at the low end of the genre, touting fake solutions to fake problems. When you believe you have found a cure for some malady, what is the next thing you need? People with that malady. And if the malady is imaginary, you first must convince people that they have it.
But if you're in Lisbon and follow the directions from Paris, you'll walk into the Atlantic.
