[slyall]

Left out Charles Hamilton

It has been estimated by the researchers Lofts and Adley that Hamilton wrote around 100 million words or the equivalent of 1,200 average-length novels, making him the most prolific author in history. He is known to have created over 100 schools that were the subjects of his stories as well as writing many non-school stories. More than 5,000 of his stories have been identified, of which 3,100 were reprinted.

https://en.wikipedia.org/wiki/Charles_Hamilton_(writer)

[Wildgoose]

Came here to say exactly this. He wrote under so many pseudonyms he appeared to be an entire team of writers on his own.