Wishing for the good ol' days when Mary-Kate and Ashley Olsen collaborated on projects instead of defining themselves individually? Well, a new book will make the two as one again.

The 21-year-old moguls are penning the coffee table book "Influence" to be published this fall for Razorbill, a division of Penguin Young Readers Group.

"Influence" features profiless of people such as artists, writers and designers who have influenced the twins and have made them the trendsetters they are today. Some of the talented individuals include shoe designer Christian Louboutin, actress Lauren Hutton, former Interview magazine editor/biographer Bob Colacello, photographers Terry Richardson and Jack Pierson and jewelry designer/sculptor Robert Lee Morris.

"Mary-Kate and I have filled Influence with the most interesting, challenging, creative people we know -- the ones who helped pave the way for us and our generation," said Ashley Olsen.

Mary-Kate Olsen added, "Our collaboration with Penguin on Influence is exciting because we are bringing something unique to the market. Ashley and I interviewed the people who have inspired us, with the hope that they will inspire and teach others."

More importantly, the book also includes exclusive photos of the twins and interviews from their personal collections.

Ashley Olsen last co-starred with her sister on the big screen in 2004's " New York Minute." Since then, she's turned on her business acumen to found the luxury brand The Row and worked with her sister with the contemporary Elizabeth and James brand.

Mary-Kate Olsen has continued to pursue her acting and completed a recurring role on Showtime's "Weeds" as well as wrapping the film "The Wackness" opposite Ben Kingsley.