Not only does Holly Keller write and illustrate her own picture books but she also creates artwork for stories by other writers, such as Paul Showers, Wendy Pfeffer and Anne Rockwood. Keller was not only known for her books featuring wonderful characters taking on real-life tasks but also has many standalone picture-books that also tell life-relating stories. Keller's Ten Sleepy Sheep was voted a Library of Congress Children's Book of the Year which was a big step for her since it was only her second published children's book.,In 1986 Keller won the Caldecott Honor 'When Francie Was Sick' and 1987 'Snow is Falling'.

Some books deal with issues ranging from adoption to fitting in, from sibling relationships to saying farewell to a beloved pet. Keller's books are not only entertaining to read, but they also have a message. She draws with a flat, minimalist and cartoon style. Keller has gotten many recognitions and awards for her books. Keller married in 1963 to a pediatrician and soon became the mother of two children. In 1981, Keller put together a portfolio of her works and submitted it to an editor at the Greenwillow Press which was where she was published using her first two books and illustrations Cromwell's Glasses and Ten Sleepy Sheep. Holly took courses at the Parsons School of Design when she finally had time and was encouraged by a professor to try illustrating children's books. As schooling for Keller continued she went on to Sarah Lawrence College to obtain a degree in history later attending Columbia University, Keller continued her history studies by earning her master's degree.

Drawing also quickly became a form of self entertainment for her. Keller was born in New York City in 1942, and was a fan of reading from an early age.

Holly Keller is an author and illustrator, who is noted for her penchant for creating animal protagonists, which she draws in a minimalist, flat, cartoon style.

The Hat by Holly Keller