I Am Einstein
Are you familiar with the "I am ... " biography series? They're written by Grace Norwich. There are a lot of titles about people from history and today. Some of the famous people that she chose to write about: Helen Keller, Walt Disney, Harriet Tubman, Cleopatra, John F Kennedy, George Washington and many others. I like this series because they're easy to read chapter books for readers at lower levels and they impart a lot of facts you probably didn't know before.
I recently read the one on Albert Einstein. I know I learned a lot about him, his family life and his work. I especially liked the top ten facts you should know at the end of the book.