If you want to read about an incredible ultrarunner you should read No Limits about ultrarunner Barbara Friedman. She's my mum's friend who I always looked up to (along with my sis) when I started running. She too came to running later in her life and I always thought it is never to late to start something new in your life.
I just finished reading about her 100 miler north of San Francisco in the Marin Headlands. It is truly inspiring.