First came the royal engagement. Now — 10 days later — the first book.

"William and Kate: A Royal Love Story," by The Sun newspaper's royal reporter James Clench was published in Britain Friday, the first in a slew of new titles about the relationship between Prince William and Kate Middleton that publishers hope will set cash registers chirping in the months before their April 29 wedding at Westminster Abbey.

Published by Harper Collins and The Sun — both owned by Rupert Murdoch's News Corp. — the book is scattered with photos by Arthur Edwards, the paper's long-serving royal photographer.

It is one of several books on the royal romance in the works. They include one by celebrity journalist Andrew Morton, whose 1992 book "Diana: Her True Story" rocked the royal family and punctured the image of Princess Diana's and Prince Charles' fairy-tale romance with its details of bulimia, depression and infidelity.

"William and Kate: A Royal Love Story" — due to be published in the U.S. on Dec. 17 — is a more reverent affair. It charts the romance between "the boy who would one day be king" and "the middle-class girl who had harbored a crush on him since her school days."

The book traces "the greatest love story of the century" from the couple's first meeting at a university in Scotland. It claims that William's nickname for Kate was Babykins, while she called him Big Willie.

Publication comes just days after the Nov. 16 engagement announcement — and at the start of the lucrative Christmas book-buying season. Clench had written most of the text in advance and turned out the final 4,000 words in 48 hours.

"The engagement was announced on Tuesday and the book was at the printer on Friday," said Anna Valentine, senior nonfiction editor at Harper Collins.

It's an increasingly common phenomenon, speeded by technology — "insta-books" appearing within days of the event they commemorate.

"Publishers have books that are ready to go," said Cathy Rentzenbrink of U.K. book store chain Waterstone's. "If Andy Murray won Wimbledon I imagine there would be a book very soon off the press called 'My Wimbledon' by Andy Murray."

Valentine said it's increasingly important for publishers to be able to move quickly with books about current events.

"Newspapers and magazines have been doing it for centuries — but if book publishers are going to remain relevant we have to be able to respond in the same way, and give consumers what they want when they want it."