My kids just loved them, but we started the series at the beginning, moved through the first few (maybe 6 or 7?), then we just decided (or maybe Mom decided!) that it was time to add variety to our bedtime reading. My special needs son saw the “prequel” called The Boxcar Children Beginning by Patricia MacLachlan (author of the Sarah Plain and Tall series), and he was curious about the story of the children with their parents before they were orphaned. Other than that, I would stick to the first 19 Boxcar Children books that were actually written by Gertrude Chandler Warner.
However, I will say that if my children were leaning towards borrowing very twaddley books from the library or from friends, I would allow the later Boxcar books instead on occasion. My youngest has a friend who recommended the Nancy Drew books, and although I don’t want her reading them constantly, I do prefer them over many other popular series books.
The Boxcar Children books are wholesome, and I think they demonstrate good character traits such as responsibility, strong work ethic, and the value of a close-knit family. The children take care of one another, they work hard to do what is needed and what is expected of them, but they also use a lot of good imagination….and they have fun without tv, video games, or electronic gadgets!