When I was in the Upper Sixth a very important thing happened. A boy called Sean Harris came to school ... He became my best friend. He had a turquoise Ford Anglia which spelled freedom for me. When you live in a village in the country driving is very important. So you can imagine that I couldn't have just any old car rescuing Harry and Ron Weasley to take them to Hogwarts -- it had to be a turquoise Ford Anglia. Ron Weasely isn't a living portrait of Sean, but he really is very Sean-ish.
-- J.K. Rowling (Conv)
Conversations With J.K. Rowling by Lindsey Fraser. The book consists of 57 pages of questions and answers followed by descriptions of the first four books. Seven pages of quotes from interviews with Entertainment Weekly, Larry King, and others fill out the end of the book.
The original English language publication was Telling Tales: An Interview with J.K. Rowling (cover image on the right)
Interesting facts and notes
The driver and the conductor of the Knight Bus ('Ernie' and 'Stanley') were named for Rowling's grandfathers. p.12
Graveyards "are a great source for names." p.15
One of the influences for Snape was a "scary" teacher she had when she was 9 years old (Tutshill, near Chepstow, South Wales). p.17
As a teacher, the "worst, shabbiest thing you can do" is to bully children (draws parallel to Snape). p.21
The characters she created the very first day were Harry, Ron, Nearly Headless Nick, Hagrid and Peeves, then she developed Hogwarts.p.37-8
JK envisioned Hogwarts as a "place of great order, but immense danger, with children who had skills with which they could overwhelm their teachers."p.38 Hogwarts
Initially there were only seven subjects to be studied at Hogwarts. p.39
Professor Lupin is a "damaged person, literally and metaphorically. [....] His being a werewolf is really a metaphor for people's reactions to illness and disability." p. 40
JK has worked out Sirius' childhood in detail. p.40
JK wrote Harry Potter and the Goblet of Fire's 9th chapter 13 times. p.88