Miaghstir: That depends on wether the books ARE the worlds, or merely links to them. As far as I know, neither stance has yet been proven right.
M15aNtHrOpE: Could you link articles on the subject (bad pun: Link worlds, Link articles)? I'm personally of the opinion that the books *are* the worlds.
No weblinked resources that I know of. Most of the information I've found in the various Myst games and books (the Books of Atrus, Ti'Ana, and D'Ni; as the Myst Reader) - and, yes, websites - have blurred together so I no longer know where I picked up each bit of information. Gehn is steadfast in his vision that he is the creator - and thus god - of the worlds he writes books for, while Atrus (the younger, not Atrus/Aitrus, father of Gehn - don't remember his stance, or even if it is revealed) and Katran/Catherine are of the opinion that there are an infinite number of worlds, and that by describing them in a "master book" (I forget what they're actually called) you merely create links to them, and then the smaller carryable (usual) linking books link to a passage within the master book and thus to a place in that world.
Also: In Myst, Atrus destroys the prison books in which his sons are trapped, but in Myst 4, they are back. (But then, some things that are said to be impossible, have been proven to be, in fact, fully possible - like linking to another place in the same world, and taking the linking book with you (both being discoveries/inventions by Yeesha, and being shown to the players in Uru.)