The statement "All conflict in literature is, in its simplest form, a struggle between good and evil." means, that any novel, when broken down is made up of two opposing forces, good and evil. Most literature is comprised of a struggle between the moral and immoral. More often than not though, the interplay between good and evil is really a matter of context, which makes the contrast between the two lines clear. This can be seen in both Lord of The Flies and Of Mice and Men. With some introspection, we see that the lines between what we think of as good and evil are often blurred as we become more engaged in the story. In the end it is left up to us to decide which is which.
In "Of Mice and Men", by John Steinback, on the surface it seems as if the murder of Lenny is an evil act.
When looked at closer, it is seen that it was an act of good. In fact, Lenny's death is viewed as a merci killing. George killed Lenny "for his own good". He knew that if he didn't kill him, the other men would have.
In "Lord of the Flies", by Sir William Gerald Golding, our initial feelings about group cohesion are positive, but by the end of the story it is the cohesion which turns then savage.