To find one book out of thousands you can look at the numbers on the edge, or the "spine label". Some have 3 digits, like 743 or 921. Others have decimals too, like 636.7 or 559.721. We call this the Dewey Decimal System after Mr. Dewey, who came up with the idea.
Once books are in number order, they are in ABC order by the author’s last name – for example, the Guinness Book of Records is 031 GUI.
Dewey Decimal Categories:
000 – 099 - How Can I Find Info On Everything? Keeping Facts Together.
Encyclopedias, Almanacs and Reference
(Examples: Guinness Book of World Records 031 GUI; I Wonder Why… 031 KIN. This also includes the Reference Section that is for use only in the library, such as yearbooks, large dictionaries and encyclopedias, etc.)
100 – 199 Who am I? Thinking About Yourself.
Philosophy & Psychology - Ideas, feelings, manners
(Example: Future Predictions 133; Optical Illusions 152; Character179)
200 – 299 Who Made Me? Thinking About God.
Religion – Beliefs around the world
(Example: Bible stories 220; Greek Mythology 292; First Olympic Games 292)
300 – 399 Who is that Person Over There? Thinking About Others.
Social Sciences - Holidays, government, careers, etc.
(Examples: US Constitution 342; US Navy 359; Easter 394.2; Real Estate Agent 333)
400 – 499 How Can That Person Understand Me? Communicating.
Languages - Foreign language and culture
(Examples: English & Spanish 419; Figures of Speech 428; Verbs & Pronouns 428.2)
500 – 599 What Makes Things Happen in the World? Studying Nature.
Science - Nature, animals, mathematics
(Examples: Apatosaurus 567.913; Forests 577; Ocean 551; Polar bears 599)
600 – 699 How Can I Control Nature? Making Life Comfortable.
Pets, farming, medicine, cooking
(Examples: Terriers 636.76; Cooking 643; Fighting Fires 628)
700 – 799 How Can I Enjoy My Spare Time? Creating Amusement.
Fine Arts and Recreation - Art, drawing and painting, music, sports
(Examples: Art, 741; Dance 792.8; Football 796)
800 – 899 What are Man’s Greatest Stories? Creating Stories.
Literature - Short stories, classics, plays, jokes and poetry
(Examples: Spooky Jokes 818; Poems for Children 811.52)
900 – 999 What Are Man’s Achievements? Recording Lives & Events.
History, Biography and Geography - Famous people, places and historical events
(Examples: Helen Keller 921 KEL; Alamo 976.4)
Note: Biography is the only numbered section which isn’t ABC by author but instead is sorted ABC by the person the book is about. Example: Ben Frankin is 921 FRA.
Easy Fiction and Fiction books (made-up stories) are organized by the author's last name.