The Boxcar Children

The Boxcar Children was initially written in 1924, but the version that everyone now knows was published in 1942, and was specifically aimed at young readers.

The book chronicles the adventures of a family of runaway orphans, Henry, Jessie, Violet, and Benny Alden, fleeing their grandfather, who they believe to be a cruel man. They eventually find shelter in an abandoned boxcar and make it their home for several months, having various adventures, before eventually being found out and returned to their grandfather's custody. He turns out to be very nice, as well as filthy rich.

After many requests, Warner followed up the book with eighteen sequels, mostly mysteries, over which the characters gradually aged. Benny, 5 in the initial book, was 11 and working as a stock boy in a department store in book #19.

Then in 1991, the Albert Whitman & Co. publishing company decided to cash in on their continuing popularity. There are now over 100 books in the series, and counting. And a cookbook, that somehow takes recipes mentioned in passing in the books and... turns them over to children. -

Contains examples of the following:

 * And Knowing Is Half the Battle: Every mystery book contained some minor science lesson, such as about plankton, or Captain Cook's voyages, or similar. A noteworthy one: Henry's sage observation that "Mashed potatoes don't smell." (The Lighthouse Mystery.)
 * Big Eater: Benny, whose catchphrase was practically "I'm hungry!"
 * Comic Book Time: Initially set in the depression era, more recent books have included passenger jets, tropical cruises, and the internet. They have a different summer adventure in every book, and they're all still young somehow...
 * Defeat Means Friendship: If the culprit of whatever mystery they're solving has any decency in him/her at all, he'll be reconciled to the Aldens right away.
 * Four-Temperament Ensemble: Benny is Sanguine, Violet is Melancholic, Jessie is Phlegmatic, and Henry, is Choleric.
 * Name's the Same: Henry James Alden is named after his grandfather, and in the first book uses his first two names as a pseudonym -- it doesn't help them hide from the grandfather.
 * Orphan's Ordeal: The whole plot of the first book.
 * Outlived Its Creator: The Boxcar Children series had only 19 books by its original creator, Gertrude Chandler Warner. Then, over a decade after her death, Albert Whitman of Albert Whitman & Company resurrected the series, producing over 100 more books due to reinterest (including a kid-friendly cookbook). Unsurprisingly, after Warner stopped writing them, continuity went right out the window. Notably, a couple pets introduced in her later books suddenly disappear, and sadly the storytelling quality does, too.
 * Parental Abandonment
 * Raised by Grandparents
 * Shrinking Violet: Violet. Hey...
 * Snap Back: Between the last book written by Warner, and the first by the publishing company, the Alden children's ages were reset to 14, 12, 10, and 6.
 * Status Quo Is God: Have you picked up what the most memorable feature of this series is yet? You can read any book past #19 in any order you like.
 * Team Pet: Watch the dog, who technically belongs to Jessie.
 * Twofer Token Minority: The Boxcar Kids get a female Korean adopted cousin.