In his famous prose work titled Areopagitica, John Milton compares reading to eating. At one point, for example, he writes as follows:
. . . books are as meats and viands are; some of good, some of evil substance; and yet God, in that unapocryphal vision, said without exception, RISE, PETER, KILL AND EAT, leaving the choice to each man's discretion. Wholesome meats to a vitiated stomach differ little or nothing from unwholesome; and best books to a naughty mind are not unappliable to occasions of evil. Bad meats will scarce breed good nourishment in the healthiest concoction; but herein the difference is of bad books, that they to a discreet and judicious reader serve in many respects to discover, to confute, to forewarn, and to illustrate.
In other words, books resemble food because some books are full of virtue and therefore have beneficial effects on those who read them, in the same way that some foods are healthy and therefore promote the health of those who consume them. Likewise, some books are lacking in virtue and thus promote vice in those who read them, just as some foods are unhealthy and therefore damage the health of those who eat them.
God gives humans the freedom to choose the kinds of foods they eat as well as the kinds of books they read. Humans have an obligation, in each case, to choose wisely, but in each case they alone are responsible for the choices they make.
Just as healthy foods can upset the stomachs of people who have weak stomachs, so even the best books can be misread, misunderstood, and misused by people who are choose to misuse and misinterpret them. (A person might even use the Bible, for instance, to justify evil thoughts and bad conduct.)
Of course, unhealthy food is unlikely to promote health in a human being. This fact distinguishes unhealthy food from bad books, because a reader who is properly motivated (seeking always to find and promote virtue) can find some good, some beneficial effect, in any book he or she reads. If nothing else, bad books can illustrate and warn against evil thoughts and evil deeds. Everything depends on the motivation of the reader.