An odd beginning to this book review: My praise is for the original editions. The modern ‘adapted for today’s reader’ or some such is a travesty of politically correct editing, and should be burnt.
Well, that over with, back to the books: The Sugar Creek Gang series is a series of explicitly Christian books about a gang of boys growing up in rural America during a much less politically correct time.
The first thing to comment on is that they are very explicitly Christian. Christianity is not in the background, it is in the foreground. While there are very few sermons from the pulpit (these usually happen off stage and are discussed by the characters later) there are typically several sermonettes: which can come from some adult figure or from one of the boys themselves.
Each of the books has some mystery or mysterious event as its tension; but the real tension is always the spiritual point that the boys need to learn while solving the mystery. So the story might involve a series of thefts; but the salvation of the thief is likely to be the actual point of the book.
As far as morally excellent books to read by or to boys, and even girls, I can hardly recommend these books strongly enough. As far as classical literature… not so much. The writing is exciting but shallow. But meaningful, always meaningful.