She was born Fannie Lou Townsend. She became Fannie Lou Hamer after marrying. She would be born to a large family (20 children) run by sharecropper parents. She did as much schooling as she could, leaving school at a young age, but continuing to read and learn whenever she could. As she grew she felt that having to work so hard for little results, the discrimination, having to struggle to take care of a family, and having no rights because she was a black woman was wrong. She realized she was the one who had to do something about it. 
And in The Story of Fannie Lou Hamer: An Inspiring Biography for Young Readers (The Story of Biographies) by Margeaux Weston is a good introduction on how that came about. Written for the older reader (at least first grade to younger fifth grade: the range is diverse as you can read to the younger audience and/or with them, or the older aged readers are perfect for the simple, but not simplistic voice). 
The subjects such as racism, death and medical content are age appropriate. They are handled well. We see the struggles of the rights to vote, the violence she faced, the discrimination and the things done towards her to try and frighten her. We see how even when she was in ill health she would still fight and advocate, even if she was not able to march or travel for speeches like she had in the past. Overall, things worked well and were not just “just the facts” but enjoyable and even entertaining. The years between October 6, 1917 and March 14, 1977 were filled with history, and Hamer was right in the middle of it all, because she was “Sick and tired of being sick and tired.”