Writing a book

I have been thinking for a few years about trying to write a book. I really feel good when I'm able to write and if I wrote a book I would be able to give myself a good excuse to write. Just the other day Peter said "mom, why don't you write a book?". We had just been talking about miscelleanous stuff and he just said it out of the blue. Then yesterday I was reading the paper and saw an article about a writer's conference in September. It is supposed to be for all levels of writers. So now I've got this idea in my head that maybe I should try to write a book...now I just need to settle on an idea of something to write about.