One element that fans of Edgar Rice Burroughs and of the John Carter of Mars series is the unmistakeable style of Burroughs. This style carries through all 11 of the books, except for the first half of the last book, John Carter of Mars. This is the story John Carter and the Giant of Mars.
While the story was originally written by Burroughs' son, Burroughs himself edited and re-wrote it. But the style is pedestrian and boring compared to the other books. Is there a reason Burroughs didn't make more of an effort to bring the style of this book more in line with his own style, which is the style fans loved so much?
NOTE: Yes, his son did the writing, but it was published under the name Edgar Rice Burroughs, not under his son's name. He's the one that is getting credit and claiming authorship as well as dealing with the blame and fallout if it's bad (which it was, by almost any measurement). Anything published under an author's name effects his reputation and his future sales as well as his popularity, so it's quite reasonable to ask why he let a book with his name go forward when the style was so weak. That all he did was edit is not a clear reason. If it was to be left as is, why not publish it under his son's name?
I have yet to see anything here that answers why an author with a reputation based, in large part, on his style, would allow publication of a book under his very own name that does not maintain the quality of the product people would have come to expect from a book with his name on it.