We should not re-read a book immediately upon the first completion but should always allow a long interval to elapse. There are several reasons for this. After an interval we acquire perspective; we are in a position to know whether a book has done us any good and just about how much. We may find after this interval that a work of which we thought quite highly at the time of reading has really not helped us appreciably either in thought or action. We may find that we have outgrown the need of it. Even if we finally decide to re-read we shall find the wait of immense help to our memory. If we re-read a book after an interval of six months, three years after our second reading we will remember its contents much better than if we had read it three times in unbroken succession. Add to this that in the lapse of time we shall have forgotten most of the work, and shall therefore approach it the second time with greater interest than if it were still fresh in mind; that our experience, reading and thinking in the meantime will make us see every sentence in a different light, enabling us to judge our own marginal criticisms (if we have made any) as well as the book, and the advantage of waiting cannot be doubted. I do not believe it will ever be necessary to read a book more than twice, that is, so far as thought and knowledge are concerned. With books read for their style or for mere amusement the case is different. How long should one read at a sitting? Some men find that their thought is choked by reading. Some find it stimulated. But results vary according to the length of time reading is carried on. Reading for very long periods at a stretch often deadens original thought. The writer finds that he nearly always derives benefit from reading for short periods, say ten or fifteen minutes. This is in some measure due to the increased concentration which short periods allow. On the other hand, some people find that a certain momentum is acquired during long reading periods. The reader can only experiment to find how long a period best suits his individual case.