When I was a kid they were written at the end of an old person's life. In the late nineties I remember the Times' book reviewer making a big deal about how Slow Motion was a new thing, a young person's memoir. That trend has grown like I don't know what. I know that it's popular with people, and with me. I know that people are making careers off of young memoirs. I know that they are some of my favorite books. Here are a few off the top of my head that I've really liked. Since I generally do go to Amazon I've tried to link to places other than Amazon to keep it interesting.
I'm Proud of You
The World's Strongest Librarian
The Reading Promise
A Broom of One's Own
Encyclopedia of an Ordinary Life