After Theodor Seuss Geisel passed away in 1991, his widow, Audrey, renovated their La Jolla home and donated most of her husband's work to UCSD.
But she set aside some doodles and sketches that were kept in a box.
Two years ago, Mrs. Geisel and her assistant contacted UCSD about donating the material in the box.
"Just thought, 'wow!' – How could we not be excited?” said Lynda Claassen, Director of Special Collections at the library.
Claassen was one of the first ones to get a look at the manuscripts and illustrations.
“I think when they found the material – weren’t quite sure what it was. They weren’t going through it page-by-page because there was a lot of material. It was kind of exciting for her also," said Claassen.
"What Pet Should I Get?" features the same siblings from another Seuss classic, "One Fish, Two Fish, Red Fish, Blue Fish."
The book's release is set for July 28.