A conservative estimate places the number of books in the world at 4,500,000. (This estimate was made before the war broke out, and the war-books by now have doubtless brought the number to 5,000,000.) This does not mean books as collections of printed sheets of paper bound together—books as physical objects—for if it did the number would be immensely greater. It means 4,500,000 (or more) separate and distinct treatises. If you were to read one book every two weeks, you would read about twenty-five a year, and if you read for fifty years you would cover 1,250. One book in every three thousand six hundred! (3,600!)

From this it is apparent that even the most omnivorous reader, even the reader who can cover a book swiftly by efficient skipping, will at least have to ask himself before beginning a volume, “Is this a book in a thousand? Can I afford to read this at the cost of missing nine hundred and ninety-nine others?” And most men who ask this question will have to substitute the number five thousand, or even ten thousand.

Nine-tenths of our reading is on mere chance recommendation, passing whim or by sheer accident. We catch sight of a book on a library table. Having nothing better to do we pick it up; we start perusing it. Every book read in this way means a sinful waste of time. To be sure, a book read in this chance manner might (accidentally) be very good—even better than some you would have planned for; but this will happen seldom, and is never a justification of the practice. By going a round about way to a place a man might stumble across a lost pocketbook, but this would not justify taking round about ways.

The first thing needed, then, is that we should plan our reading. Perhaps the best way to do this would be to make out a list of the books we intend to read for the coming year, or say a list of from a dozen to twenty-five volumes, and then read them in the order listed. Another good plan is to jot down the title of every book we intend to read, and keep the list about with us. Then when we meet with a book which we think would be good to read, or which we feel we simply must read, we can before starting it glance at our list. The formidable array we find there will probably induce us either to give up entirely our intention to read the book before us, or at least to put it somewhere on the list which will allow more important books to be read first.

Some people cannot endure planning their reading in this manner. It grates on them to think they are tied down to any sort of program; it seems to deprive them of the advantages of spontaneous interest. Well, if you cannot plan your reading prospectively, at least plan it retro­spec­tive­ly. If you cannot keep a list of books you intend to read, at least keep a list of books you have read. Refer to this from time to time. See whether you have been reading uniformly good literature. See whether you have been reading too much on one topic and not enough on another, and what topics you have been long neglecting. But at best this method is a poor substitute for planning your reading prospectively.

We should plan not only with regard to topics and subjects, but with regard to authors. Obviously if two men of equal ability both study the same subject, one will get more out of his study than the other if he reads authors who treat the subject on a deeper plane—provided of course he understands them.

Whether consciously or not, we tend to imitate the authors we read. If we read shallow books we are forced, while reading them, to do shallow thinking. Our plane of thought tends toward the plane of thought of the authors we study; we acquire either habits of careful critical thinking, or of dogmatic lack of thinking.

This emphasizes the importance of reading the best books, and only the best books. Our plane of thinking is determined not alone by the good books we read, but by all the books we read; it tends toward the average. Most men imagine that when they read a good book they get a certain amount of good out of it, and that this good will stay with them undiminished. Provided they read a certain number of serious books, they see no reason why they should not read any number of superficial or useless books, or any amount of ephemeral magazine or newspaper literature. They expect the serious reading to benefit them. They do not expect the shallow reading to harm them. This is just as if they were to buy and eat unnutritious and indigestible food, and excuse themselves on the ground that they ate nourishing and digestible food along with it.

The analogy may be carried further. As it is the average of the physical food you digest which ultimately determines the constitution of your body, so it is the average of the mental food you absorb which determines the constitution of your mind. One good meal will not offset a week of bad ones; one good book will never offset any number of poor books. Further, as no one has a perfect memory, you do not retain all you read any more than you retain all you eat. Therefore if you do not want your mind to retrogress, you should not rest satisfied with books already read, but should continue to read books at least as good as any previous. As at any given time your bodily health—so far as it depends on food—is mainly determined by the meals of the last few days or weeks, so is your mental health dependent on the last few books you have read.

One of the first things we should look to in selecting books is their comp­re­hen­sive­ness. To quote Arnold Bennett: “Unless and until a man has formed a scheme of knowledge, be it but a mere skeleton, his reading must necessarily be un­phi­lo­soph­i­cal. He must have attained to some notion of the inter­re­la­tions of the various branches of knowledge before he can properly comprehend the branch of knowledge in which he specializes.”[23] As an aid in forming this scheme of knowledge, Mr. Bennett suggests Herbert Spencer’s First Principles. I heartily endorse his choice. I would add to it the essay on The Clas­si­fi­ca­tion of the Sciences by the same author.