In addition to the expected dictionaries, thesauri, encyclopedias, etc. Don's books has a more than complete, compelling array of reference materials.

Domestic Reference

Cleaning, Housework, Etiquette, Weddings

Study Reference

Study Guides, Book Notes, Test Preperation

Communication Reference

Writer's Guides, Style Guides, Writer's Resources, Public Speaking, Quotations.

Mythology

Mythology, Fairy Tales, Folklore.