An illustration is an enlargement, an interpretation of the text, so that the reader will comprehend the words better. As an artist, you are always serving the words. You must never illustrate exactly what is written. You must find a space in the text so that the pictures can do the work. Then you must let the words take over where words do it best. It’s a funny kind of juggling act.
As an aspiring artist, you should strive for originality of vision. Have something to say and a fresh way of saying it. No story is worth the writing, no picture worth the making, if it is not a work of the imagination. ~Maurice Sendak