Ashurbanipal

Ashurbanipal (最古図書館) is the Grand Library that's located at the 10th Floor of the Great Tomb of Nazarick.

Background
Ashurbanipal is the great library of Nazarick, wherein Nazarick's great wealth of knowledge is placed.

Most of the books in the library of the Great Tomb of Nazarick are summoning books. In reality, there is no need to acquire so many books, as using every single resource from Nazarick, one cannot summon even a tenth of the amount of monsters.

Because the monster data was not very expensive, the guild members started making a massive number of duplicates. Therefore, the true reason for gathering so many books was to hide important magic items by blending them among the ordinary ones making it impossible for anyone other than guild members or servants to find anything.

Though the library of Nazarick contained data on various types of monsters, it did not contain the data of every single type of monster hailed from YGGDRASIL. Some monster's data were of limited use too. For example, Nazarick had already exhausted their supply of data on Hanzos and the library did not contain any data for the creation of Eight-Edge Assassins. The creation of higher-tiered monsters would incur the cost of a large sum of gold.

The books in the library can be mainly put into five categories:
 * 1) A collection of recorded monster data, which was required to summon said monsters such as mercenaries. There are three types of monsters inside Nazarick The first type consists of monsters that are created in a similar manner as player characters. The next type consists of automatically spawning monsters that are under level 30, and the last type consists of monsters up to around level 80 that are summoned as mercenaries like Hanzo. Mercenary monsters need to be summoned using a book, a special summoning ritual, and an adequate amount of gold. Thus, they cannot be summoned without a book.
 * 2) A collection of magic items and certain data crystals that can only be imbued into a book-shaped object. Items shaped like books usually tend to be single-use magic items. The difference between a scroll and a book is that while scrolls can only be used by certain classes, anybody can use bookmaking them more useful and valuable.
 * 3) A collection of event items, which are not uncommonly required when advancing into a special class. These can be items required for class changes, items for race changes, learning new magic, and books for studying about skills and legends. Additionally, some of these items come in the shape of a book.
 * 4) A cosmetic skin database. These books contain the cosmetic skin data of objects like swords, shields, and armor. Thus, players with certain blacksmith skills can put new skins on items and other appropriate materials.
 * 5) A collection of novels in the form of book-shaped items. Normally, there would be old and classic literature whose copyright ran out a long time ago, but there are also background stories distributed by the development team, and original novels written by players in YGGDRASIL. There is a number of fanfictions based on the worlds of YGGDRASIL or game guides in the form of diaries or novels.

The Emissary of the King Arc
Ainz Ooal Gown visited the library under the guise of doing research, instead, he wanted to brush up on his management skills and decided to take-out some self-help books. He had to take out several stacks of books to acquire only two books so that he would not reveal his insecurity to the library staff.

The Show Must Go On! Arc
Albedo was searching through several book stacks for a play to use in Nazarick's first theater production. During the midst of her research, she came across the manuscript of the "Romeo and Juliet" play to assist her with the acting.

The Two Leaders Arc
Mare Bello Fiore visited the Great Library to seek permission from Titus Annaeus Secundus to borrow his Overlord guardians.

Table Game to Understand Humans Arc
Ainz Ooal Gown silently sneaks into the library of Ashurbanipal to return his borrowed business books after he finished reading it. Along the way, Ainz had stumbled upon a rulebook for a tabletop game. It apparently seems that the book has been added to the library thanks to Tabula Smaragdina's effort, according to Ainz. Flipping over several pages, Ainz came up with an idea on how it can help him with getting the Floor Guardians to play a table game as an exercise to better understand humans.

The Magic Caster of Destroy Arc
According to Lupusregina Beta, she was not able to find any worthwhile lower-level goblins in the library. Instead, she was left with no other choice but to result in summoning forth at least level forty-three goblins from that location. Since there is no goblin variants lower in levels than forty-three, Redcaps were considered to be the bare minimum that Nazarick have in their arsenal for killing off the remnants of Prince Barbro's forces.

Layout & Features
The wide front door of the library is guarded by two high-class golems. The library itself is well-groomed, displaying a lot of art pieces and decorations covering every corner of the library. Resembling something similar to an art museum, even the ceiling is adorned with a beautiful painting. There is also a 2nd Floor in the library with a lot of glass shelves orderly placed. It is very much this way that almost all of the shelves cannot be visibly seen in a single glance. There are also several smaller rooms designed for specialized uses and the individual rooms for the staff. There are three major corners in the library:
 * Room of Logic
 * Room of Wisdom
 * Room of Magic
 * Crafting Room: This room is where magic scrolls are produced. Inside it is a workshop containing countless materials of great quality and quantity, which are used in manufacturing magic scrolls.

Literary Collection

 * Alice's Adventures in Wonderland
 * Anecdotes of the Four Great Spirits
 * Being A Boss For Dummies: Tips And Tricks On Becoming A Respectable Boss Book
 * Bibliography of Weapon Research
 * Book of the Dead
 * Deputy Student Council President Is A Charismatic And Number One Maid!? ~ Regardless of Criticism ~
 * Economics That Elementary School Students Understand
 * Hack And Slash Adventure
 * Halloween Festival
 * Living With Hamu-chan! An Encyclopedia For Raising Hamsters
 * Ninya's Diary
 * PKing for Dummies
 * Romeo and Juliet
 * Snow White
 * The Adventures of Tom Sawyer
 * The Secret of Building Trust With One’s Subordinates
 * The Tale of the Bamboo Cutter
 * The Tale of the Heike
 * The Three Visits
 * The Wizard of Oz
 * Things That Hated Bosses Don't Do
 * Your Ally Glitter ★ Magic Book

Known Characters from Ashurbanipal

 * Titus Annaeus Secundus
 * Librarian J
 * Aelius
 * Aurelius
 * Cocceius
 * Fulvius
 * Ulpius
 * Protagonist (Mass for the Dead)

Trivia

 * Ashurbanipal is heavily guarded by the five Overlords of the Grand Library in Nazarick.
 * There are multiple spirits and elder liches working there in the library tending to its many needs.
 * Titus conducts his research and experiments in this library.
 * Tabula Smaragdina was known to have added many esoteric works from all over the world in the library.
 * The library is a reference to Ashurbanipal, the last great king of the Neo-Assyrian Empire known for its collection of clay tablets.
 * In Mass for the Dead, the library was heavily damaged after the transfer into the New World though the contents within survived and is under the care of the protagonist.
 * The NPCs of Nazarick use Ashurbanipal to research several holiday celebrations mentioned by their master. For instance Hanami and also Christmas.