"the "Wizard of Oz" (the book) was a very adult, bitter, POLITICAL satire"

Only one of many otherwise long tedious boring books (that no sane child would read today) that would have sunk without a trace by the same author without the film having been made.

Oh, and then there's "The Princess Bride" - another one of many otherwise long tedious boring books (that no sane child would read today) that would have sunk without a trace by the same author without the film having been made.

(Note: insert other examples ad tedium ...)

One has to ponder whether the makers of these films (and many others like them, also based on other authors who would have otherwise sunk totally without trace today) did a good thing to keep those authors alive - well, more likely mummified - or, by making those movies, did they do something more akin to Shakespeare who took some old tales (which most of us would have never heard of today) and breathe into them some new sort of life as a new product on their own ....