Even though he passed away in 1991, Dr. Seuss' legacy lives on with his classic children's books. Thanks to newly discovered manuscripts and drawings, a new book by the author will come out.

USA Today reports Seuss' widow, Audrey Geisel found materials at the author's home in La Jolla, California. These materials will help Random House Children's Books publish "What Pet Should I Get?" which will be released July 28, and at least two more new Dr. Seuss books.

Theodor "Ted" Seuss Geisel's widow Audrey found a box filled with pages of writings and sketches when she was remodeling their house after his death. She set the box aside. In 2013, that box was opened by Audrey and Seuss' longtime secretary Claudia Prescott while two were cleaning out Seuss' office.

Audrey and Prescott found the full text and drawings for "What Pet Should I Get?" and other writings and drawings.

"While undeniably special, it is not surprising to me that we found this because Ted always worked on multiple projects and started new things all the time -- he was constantly writing and drawing and coming up with ideas for new stories," Audrey said in a statement.

Audrey says it is special for her that she found the plans for "What Pet Should I Get?" because this year marks 25 years since Dr. Seuss' last book "Oh, the Places You'll Go!"

When Audrey found the box, she knew it was something big. She knew it was "more than just a box of sketches."

It is estimated that Seuss wrote "What Pet Should I Get?" sometime between 1958 and 1962, according to Random House associate publishing director Cathy Goldsmith.

"What Pet Should I Get?" includes the same brother and sister from Seuss' 1960 book "One Fish Two Fish Red Fish Blue Fish," according to ABC News.