My previous post received some comments that I think deserve further consideration. How many of the books we loved as children stand up to adult reading? Why? Does it matter?
For me, the L.M. Montgomery books do stand up...as long as I don't overdose. There are certain themes in the books that get repeated -with different characters- in each book. When given adequate time between reading, I don't find this a problem, but I'm certainly aware of it.
For really young children-- if I can read a book over and over to a child without thinking it banal...I (as an adult) rate it an excellent children's book. Children, however, often love to have books read to them over and over that an adult will consider boring and trite (driving said adult to distraction at the 3rd reading, much less the 203rd demanded by said child). If the book appeals to many children in the same way, then logically, it must have qualities that place it above the dull category into which an adult might consign it.
For early readers-- being able to read on their own in such a reward in and of itself for children. Having characters that can be counted on to remain the same (I don't think young children want character growth nearly as much as they want dependability), but who continue having new adventures is a plus for beginning readers.
Another note, I remember when my children fell in love with the Sweet Valley High series. I was stunned, horrified! Their reading levels so much higher and there were so many excellent books available, why did they turn to these silly things? Obviously, I was too old to appreciate whatever call these books had. I, who would not have blinked an eye had they been reading Nancy Drew. Which tells me something... I read Exodus, Gone with the Wind, and other adult books in grade school, and I adored Nancy Drew. At the same time.
Poetry is the same way. I still love some of the poems I read in childhood. They are not good poetry, and I'm perfectly capable of distinguishing between the quality of "Little Boy Blue" by Eugene Field and "Holy Sonnet 10" by John Donne. I love them both. I read Donne as a child (in one of my mother's anthologies), but I couldn't appreciate him. Maybe Eugene Field is partially responsible for creating a love of poetry that was capable of growing and maturing. In my book, that makes Field as important as John Donne.
So... does it matter if The Boxcar Children would not stand up to a re-reading from an adult perspective? Not for me. It was a step on the way and will always evoke feelings of comfort and satisfaction and gratitude.