Source: Eberron - Rising from the Last War

Wondrous item, common

This polished Eberron dragonshard fits in the hand and stores information similar to a book. The shard can hold the equivalent of one book that's no more than 320 pages long. A shard can be created blank or already filled with information. When the shard is created, the creator can set a passphrase that must be spoken to access the information stored within.

While holding the shard, you can use an action to open your mind to the shard, seeing its content in your mind. On subsequent rounds, reading the text or scribing new text on blank "pages" in the shard requires concentration (as if concentrating on a spell) and takes the same amount of time it takes you to read and write normally. Thinking of a particular phrase or topic draws you to the first section in the shard that addresses it.

A wizard can use a spellshard as a spellbook, with the usual cost in gold and time to "scribe" a spell into the shard.