Scattered reading confuses more than it teaches. Many books, even good ones, have the same effect on the student.

Martin Luther on Reading Books:

A student who doesn’t want his work to go for nothing ought to read and reread some good author until the author becomes part, as it were, of his flesh and blood. Scattered reading confuses more than it teaches. Many books, even good ones, have the same effect on the student. So he is like the man who dwells everywhere and therefore dwells nowhere. Just as in human society we don’t enjoy the fellowship of every friend every day, but only of a few chosen ones, so we ought to do in our studies. – Between January 2 and 26, 1533