Our first thought when reading fiction books from Grace & Truth was, "In the whole history of mankind, has anyone actually talked this way?" The answer is probably irrelevant, but it relates to another question about these Victorian Era character-building stories: "Does anyone, even the most godly Christian, really act and think this way all the time?"
There are three series of books from Grace & Truth: the Girl's Heritage Series and the Boy's Heritage Series feature stories for and about girls and boys respectively, while the Character Building Collection is less gender-specific. All the stories in all three series are character building tales about Christians old and young who deny themselves in order to serve the Lord and bring others to saving faith through evangelism and quiet witness.
The writing in these books isn't great, but it's definitely better than many of the character building stories from the same period. The dialogue is stilted, but because the authors were more concerned with imparting biblical truth than with entertaining audiences the prose clips along without the plethora of mundane detail that weighs down so many similar efforts.
Not that everything touted as "biblical truth" actually is; these books tend to moralize and rely on man-made rules as guides for behavior rather than on God's Law. Also, the heroes and heroines tend to be better than human beings ever can be. By not showing characters realistically, the authors run the real risk of making those outside the faith think one has to be perfect to enjoy God's grace, and those within the faith that they're not very good Christians because they aren't perfect.
In fact, Christian doctrine is rooted in man's imperfection, his fallibility and propensity for sin—we are saved by Christ because we're sinners, not because we're pure either before or after we've accepted Him in faith. Still, if you want your kids to read but (legitimately) disapprove of the commonly immoral or unchristian books for young people, these can offer a refreshing respite from worldly literature.