The Dark is Rising/ The Seeker.
Christopher Eccleston (The Black Rider): "When I read the book..."
Interviewer: "You must've been the only one on that project who did !"
The book was so badly mangled that it lead the elderly Susan Cooper to the brink of suicide, until the backlash from three generations of infuriated fans. It struck me personally because this sequence was the, "Harry Potter," of its day. I was one of the fans who waited breathlessly for, "The Grey King," and, "Silver on the Tree." (Much the same way as my parents' generation awaited, "The Chronicles of Narnia.")
The charming book with the large, chaotic, but close-knit Stanton family, the Buckinghamshire countryside, and the record-breaking winter that precedes 13 year-old Will's transformation into the last of the Old Ones, becomes a transplanted American family, with a bullying older brother, a brattish younger sister (Will is the youngest in the book, Mary is motherly, and Gwen is bossy), and - of course - Will is no longer the seventh son of a seventh son (His eldest brother, Tom was stillborn) because the director couldn't understand the reference, and didn't think his audience would either.
Of course, it didn't help that everyone decided it was a rip-off of Harry Potter, despite the first book, "Over Sea, Under Stone," being written before JK Rowling was born, and "The Dark is Rising," and, "Greenwich," being published before she was out of nappies.