Books in this set read like the Second Great Lesson — facts are presented within strong, engaging stories covering the key Time Line of Life presentation points. Includes 6 books, one for each era on the Time Line. Written by Montessorians Doug and Claudia Mann and designed as an extension to the Time Line of Life, this set offers children many opportunities to solidify their understanding and expand their research. Invaluable additions to your library, all books are updated with current terminology and scientific developments. Paperback. Ages 6 to 9.