Books were made from specially-formulated paper, using a recipe that was closely guarded by the Guild of Books. This paper was then bound into a hardcover leather volume using another special process, creating a blank Book, or kor'nea (Kor'nEa). These Books were then given to the Guild of Writers, who used them in regestoy—the Art of writing Ages.
The ink used to write Books was also special, and its formula was held by the Guild of Ink-Makers. The complete ingredient list is unknown, but there is evidence to suggest that one of them was crushed scarab beetles.
The precise processes for manufacturing Books is currently unknown to humanity, despite years of research by the D'ni Restoration Council. However, the practice does still survive on Releeshahn, amongst those D'ni who survived the destruction of their civilization.
The linking panel is a rectangular "window" which shows a visual depiction of the Age to which the Book links. These panels can be located anywhere in the Book, but are typically found at the beginning for ease of access. Some Books, like those used in the Nexus, have a panel in the middle of the Book, possibly to facilitate more even wear on the Book's spine over many openings and closings.
Contrary to evidence in the Myst games, sound cannot travel through a linking panel, nor can someone on the other side see "out" of the panel as though it were a floating window.
The image in the linking panel is referred to as the "gateway image". This image is often moving in some way, though this is not universal. The behavior of the moving image itself is also not universal. Some images' viewpoints orbit around the link-in location, others perform a "fly-by" of the surrounding area before settling into an orbit, and still others show a single "fly-by", after which the viewpoint comes to rest at the link-in location.
Types of Books
A Descriptive Book is where a Writer fully describes the Age to which they wish to link. These volumes are typically very large, with a considerable number of pages in them, suitable for the extensive descriptions needed to craft a stable link. There can only ever be one Descriptive Book for an Age. Because regestoy is capable of accessing the infinite possibilities of the quantum mechanical multiverse, it is highly improbably (though not strictly impossible) for two Descriptive Books to ever link to the same Age, even if their descriptions match exactly. There are always too many variables left undefined to guarantee that a link is forged to the same place twice.
Because Descriptive Books contain the only full copy of an Age's description, they tended to be very heavily protected by the D'ni. Damaging or altering a Descriptive Book could cause the Age to become unstable, shift the link to a similar but distinct Age, or even cause the link to stop functioning altogether. For this reason, the Books typically found in public libraries were Linking Books (see below), while the Descriptive Books were kept in a more secure area.
The term Linking Book has become something of a catch-all for any kind of Book. This can lead to some confusion when trying to interpret historical accounts, as it is sometimes unclear whether the object being described is a Linking Book or a Descriptive Book. Formally, "Linking Book" specifically refers to a smaller volume which can be used in lieu of a Descriptive Book. However, if a Descriptive Book is destroyed, any Linking Books connected to that Age will cease to function.
Unlike Descriptive Books, there can be an unlimited number of Linking Books associated with a given Age. Additionally, while a Descriptive Book transports its user to the place it describes, a Linking Book transports its user to the place where it was written. Even though a Linking Book has some connection to an Age through its Descriptive Book, a Writer doesn't need to know anything about the Age's Descriptive Book in order to write a working Linking Book that brings them back to that location. It is not presently known what exactly needs to be written into a Linking Book to make it function.
A tale describing how Books were first invented appears in the canceled Myst comic books—specifically, Myst: The Book of the Black Ships issue 0. In it, a D'ni Guild Master named Varsil developed them to solve a famine that had ravaged the D'ni people for two generations. This story has been declared apocryphal by RAWA, as it conflicts in many ways with established D'ni history.
The games Myst and Riven depict a special type of Book called a Trap Book. Atrus describes these Books as ones where the link is partially severed, causing the user to become trapped in limbo between Ages. If another person uses the Book, the original user is displaced back into the originating Age, and the new user becomes trapped. The Red and Blue Books (Spire and Haven) in Myst and the Book used to capture Gehn in Riven are all Trap Books. However, this kind of Book does not actually exist.
In a 2000 email to the Riven Lyst community email listgroup, RAWA explains that Trap Books were an invention that Cyan developed in order to simplify the gameplay of the first two games in the series. Historically, these would all have been prison Ages—Ages with no Linking Books in them—and the Stranger would have needed to rely on other kinds of information to successfully complete the tasks of freeing Atrus from his prison on K'veer in Myst, and trapping Gehn in a similar prison in Riven. Indeed, Myst IV: Revelation abandons the Trap Book notion entirely, and fully fleshes out the appearance of the Ages in which Sirrus and Achenar were imprisoned for almost 20 years.