By Genre:
* Fiction: Novels, short stories, poetry, plays, graphic novels, etc.
* Non-fiction: History, science, biography, philosophy, self-help, travel, etc.
* Textbooks: All levels, from elementary to university.
* Children's Books: Picture books, chapter books, young adult fiction, etc.
* Art & Photography Books: Fine art, photography, design, etc.
* Music Books: Sheet music, biographies, histories, etc.
By Condition:
* New: Brand new books, sometimes at a discount.
* Used: Books in various conditions, from like-new to well-worn.
* Rare & Collectible: First editions, signed copies, limited editions, etc.
Other Categories:
* Maps & Atlases
* Postcards & Ephemera
* Autographed Books
* Out-of-print Books
* Foreign Language Books
* Antiquarian Books (very old and rare)
Essentially, if it's a book, you'll likely find it on Abebooks.
To explore their vast selection, you can browse by category, keyword search, or even search by ISBN.