This article (here) Keeping the Noraholics Happy by Alexandra Alter that I read and then had forwarded to me by a former employer speaks to that astounding prolificness. The first few paragraphs say it all:
Romance writer Nora Roberts didn't bother to celebrate when she finished her 200th book, "The Witness."
"I don't really count," says Ms. Roberts, a 61-year-old grandmother with red hair and a gravelly smoker's voice.
She took a couple of days off to catch up on chores and gardening. Then she launched into her 201st, "Celebrity in Death," the next installment of a futuristic romantic suspense series that she writes under the pen name J.D. Robb. She's since finished her 202nd, a romance novel set near her home in Maryland, and her 203rd, "Delusion in Death," another J.D. Robb book. She's now writing her 204th, "Whiskey Beach," a romantic suspense novel set in coastal Massachusetts.The passage that I like, and I've always enjoyed passages like this, speaks to how she got started. Sort of like the J.K. Rowling, sitting at home making up stories for her children story line.
Ms. Roberts was raised in an Irish Catholic family in Maryland. She began writing one day in 1979 during a blizzard, when she was stuck home with her two young sons. Silhouette, a romance imprint, published her debut novel, "Irish Thoroughbred," in 1981. Over the next three years, she published more than 20 novels. Her books broke traditional romance conventions: They featured non-virginal, flawed heroines, ensemble casts and snappy dialogue tinged with sarcasm, and were occasionally written from the hero's point of view. Her unconventional stories helped transform the genre, which has exploded into a $1.4 billion industry.
Its alot like Janet Evanovich just on an even grander scale. Probably not the best writing, but it appeals to so many you have to be awed by it.