Book suggestions will probably be helpful about in proportion to the outsider's knowledge of the mind and soul of the person to be helped

From A Book Lover's Holidays in the Open by Theodore Roosevelt, 1916. Chapter IX. The entire brief chapter is worth reading in its entirety.

I am sometimes asked what books I advise men or women to take on holidays in the open. With the reservation of long trips, where bulk is of prime consequence, I can only answer: The same books one would read at home. Such an answer generally invites the further question as to what books I read when at home. To this question I am afraid my answer cannot be so instructive as it ought to be, for I have never followed any plan in reading which would apply to all persons under all circumstances; and indeed it seems to me that no plan can be laid down that will be generally applicable. If a man is not fond of books, to him reading of any kind will be drudgery. I most sincerely commiserate such a person, but I do not know how to help him. If a man or a woman is fond of books he or she will naturally seek the books that the mind and soul demand. Suggestions of a possibly helpful character can be made by outsiders, but only suggestions; and they will probably be helpful about in proportion to the outsider's knowledge of the mind and soul of the person to be helped.

Of course, if any one finds that he never reads serious literature, if all his reading is frothy and trashy, he would do well to try to train himself to like books that the general agreement of cultivated and sound-thinking persons has placed among the classics. It is as discreditable to the mind to be unfit for sustained mental effort as it is to the body of a young man to be unfit for sustained physical effort. Let man or woman, young man or girl, read some good author, say Gibbon or Macaulay, until sustained mental effort brings power to enjoy the books worth enjoying. When this has been achieved the man can soon trust himself to pick out for himself the particular good books which appeal to him.