There are a number of reasons a book can be considered a rare book.
Scarcity
Age and Imprint
Importance
Association
Aesthetic or physical quality
SCUA currently possesses 55,000 rare volumes, focusing on agriculture, science, and technology.
Collection Strengths
Main collection strengths:
Agriculture
Science
Technology
Secondary collecting areas:
Artist’s books
Costume dress, and fashion
Domestic science, home economics, and household management
Incunabula, or books printed before 1501
Iowa Cookbook Collection
Iowa and local history
Literature: includes the Margaret Young Science Fiction Collection, several Charles Dickens novels in original parts and first bound editions, works by Lafcadio Hearn, and G.A. Henty novels.