AKA National Novel Writing Month. I've been taking part in this for years. Basically you write 50,000 words in 30 days. I've done it every year for the last 8 years except last year (cos I was in Singapore for the wedding) I've never achieved the 50k although one year I did get to about 30k. You aim for 1667 words a day, no editing, no re writing. You just write. I usually write a Mills and Boon type of romance novel. People can be scornful of romance novels but it's a bulti million dollar a year industry!
This year I'm trying a semi autobiographical woman's fiction book about a woman who has to deal with the breakdown of her long marriage and how everyone has an opinion it and what she should do. They say write what you know!!! It's funny as well as downright awful in places. Bit like my life really ;-)