No one wants their kids reading complete trash. It's pretty widely understood that what goes in comes out, and if kids consume a steady diet of books with bad morals, chances are they're going to retain those attitudes, regardless of the instruction they get at home. Wouldn't it be better to have them read books with clear messages of Christian virtue and well-behaved main characters?
Yes and no—obviously, we want good examples set for our children, and character-building stories often provide them. At the same time, they have a tendency to portray their heroes and heroines as too good, so that kids see a completely unrealistic picture of childhood which they consequently reject, if not at home, then later in life when it matters even more.
In the Bible, of course, Jesus Himself is presented as our example for leading a godly life. The difference is that these books are supposed to be representations of ordinary people, not the Son of God. To suggest that human beings (especially children!) can attain a state of near-sinless perfection is dangerously close to heresy.
That said, even stories of this kind are better than a lot of the available reading material for youngsters. If the goal is to raise children in the fear and admonition of the Lord, giving them an unattainable standard is superior to giving them one far too easily achieved, or none at all. Stories about selfish kiddos, kiddos who get their way, kiddos who are more wise than adults—these aren't the kind of stories our impressionable tykes need to read.
With that in mind, we offer wholesome fiction. A lot of these books are Victorian-era novels highly influenced by the moralist tones of the period, but many are also more recent ventures (and also a little more realistic). We suggest you not make a steady diet of these sorts of books (they don't typically feature the best writing), but every now and then it's not a bad idea to refresh your children's pool of good examples.