The protagonist of my gift basket designer series is a woman just a few years younger than me who lives in my hometown of Colorado Springs, so I'm writing what I know, mostly, for her character. She IS different than me, however. I say she's braver than I am and I'm smarter than her. For the second book, TO HELL IN A HANDBASKET, though, I tried out a number of things that I didn't know about for research: snowshoeing, riding a snowmobile, visiting a grunge snowboarder bar, interviewing an Undersheriff, etc. And yes, if all I wrote was what I already knew, it wouldn't be much fun. :)
I wrote an American novel, as that is what I tend to read. I got an agent on the back of it, but I couldn't get placed. Then my agent told me to "write what I know". I did, wrote a UK novel, and got a publishing deal pretty quickly.
What surprised me was how much the publishers were interested in me as a criminal lawyer, not just as a writer. I think the reasoning is that who would buy a legal thriller from someone who works in a baked bean factory? The reader couldn't rely on the truth of what they were being told. If the person who worked in a baked bean factory wrote, however, about someone who works in a factory and witnessed a crime, etc, it would still sell.
For me, "write what you know" was the best advice I ever received.
The fact that I used to do what my main character does has been one of the main focus points of every interview I've done. It has really helped me sell myself and the book.
Whilst that's a different point to 'write what you know' I'm sure it helped my publishers take a chance on me as they knew they could market me effectively.
Yeah I can understand that publishers also need a hook with the author as well to sell the book, at the end of the day it is all about money for them, and if the author cannot be sold, neither can the book, but I tend to think everyone has an interesting life, you can make anyone interesting, everyone has something that makes them stand out whether they realise it or not. Going against the grain for a sec though and look at an author such as Mark Billingham, he writes about crime, and in my opinion is a great author, but he has no link to police really. He is a comedian/actor, which is probably why he was an interesting proposition for the publishers in the first instance. I did however hear that he was robbed at gun point once, don't know how accurate that information is though. I spent 4 years in the police and have worked with children in America, this is probably why I wrote my novel, but I don't think that wthout these experiences I could not have written the the story, so perhaps publishers and literary agenices should be more open. I wonder how many excellent novels go unpublished because of the old addage 'write what you know'. What about sci Fi, storys like Jurassic park, are these authors writing what they know?? No, they are just very good storytellers, and at the end of the day it does not what how much you know. If you cannot tell a story in a way to appeal to a varied market it won't sell, plain and simple.
I have never liked the use of an author to sell a book. It's the book that should sell the reader and make him buy another book by the same person. Why should it matter what an author looks like, if he/she is married, divorced, single, gay, heterosexual, young, middle-aged, or old? But people care about pets, hobbies, professions, weird jobs, weight, hair, food addictions, religion, party affiliation, and all sorts of totally irrelevant things. Read the books, for God's sake! If that isn't enough, maybe the reader should switch to another author.
I've been able to use my publicity to raise awareness of the issues in the book about children in care. I've only been able to do this because I've been marketed as an expert. But if it means more people become aware why would I care?
You only have to look at two of the most successful crime writers: John Grisham and Patricia Cornwell.
John Grisham writes legal thrillers. If I read one of his books, I feel I can rely on its accuracy, and it gives the book integrity. Similarly with Patricia Cornwell.
However, there is a downside. Although I am a criminal lawyer, I shied away from a legal thriller, as I would become obsessed with the accuracy of the fine detail and stop focussing on the plot and characters and all the other things that make a book interesting. I write crime thrillers, not legal thrillers, so I can work in an area that I am comfortable with, but not become uptight about the fine detail.
So, yes, write what you know, but remember that the reader doesn't need to know everything that you know. Also, the question to be asked is not whether something "would" happen, but whether it "could" happen. Two different questions, with two different answers.