A Linking book (D'ni language: Korvahkh) is a book written according to the Art, complementing and facilitating the usage of a Descriptive Book and linking to an Age. Like the Descriptive Books, the Linking Book featured a Linking Panel.
Linking Books make linking more convenient and portable. A Linking Book is simply written as a reference to a Descriptive Book, with a common combination of paragraphs and descriptions pointing to the original Book; no phrases are needed in the Linking Book from any Descriptive Book.
Whereas only one Descriptive Book can exist for an Age and can't be duplicated, multiple Linking Books can be writen referring to a Descriptive Book and an Age. The Descriptive Book can be stored and protected (until used for reference and changes) while its Linking Book(s) can be carried and safely lost or destroyed. They were quickly written and were by nature smaller, more portable and more economical in paper and ink.
Linking Books were placed in protected places of a visited Age so that one could always return to the Age of their origin. Travelers usually carried a spare Linking Book just in case something had happened to the return book.
There were cases when Linking Books required some power to functional. The Book to Selenitic was powered by machinery, although its details were obscure. Gehn had to power mechanically his defunct Books with his dome network.
A property of the Linking Books was that they had to be written in the Age, and on the very location they were supposed to link to. Atrus wrote the Myst Linking Books in the Myst Library; as he took them with him to his Ages, whenever he linked back to Myst, he always returned to the Myst Library. Gehn was able to write five Riven Linking Books on each of the islands of Riven (at the site of his domes), and thus could link to each of them from his 233rd Age. It is notable that Gehn could write his Linking Books even while his original Riven Descriptive Book was in another Age (in this case, K'veer in D'ni), inaccessible to him, provided that he had the appropriate references at hand.
However that doesn't mean that Linking Books can be used to link directly from one point in an Age to another point in the same Age; the act of linking by definition implies dimensional transfer. This means that while one is in the City of D'ni|D'ni City, even if they held a Linking Book written in Ae'gura, they could never use it to "teleport" to the island, as the Linking Book and the destination exist in the same Age (Earth) at the same time.
As Linking Books contain references to preexisting Descriptive Books, they are heavily depended on them; if major alterations were made to the Descriptive Book, and its link redirected to a closely resembling Age, chances are that its Linking Book(s) would be rendered useless. Needless to say, that this was the case when a Descriptive Book was destroyed altogether.
Linking Books can be rendered useless when damaged (eg. when a page is removed). Sirrus and Achenar took a page from their father's Myst Linking Book, and he was stranded in K'veer, unable to return to Myst.