Good but....?? (spoiler!)

You really only need Myst and Riven to understand it - Exile doesn't really refer to it at all, and Revelation sort of alters the story to some degree... but it's not necessary to understand the story from the earlier perspective.

Basically (and I WILL be using some spoilers here), before the Myst games begin, Gehn is trying to hunt Atrus down, to learn how Atrus is able to write stable Ages while all of Gehn's eventually decay. Gehn captures Catherine - a girl of the Age of Riven (which Gehn is using as a base of operations) who Atrus has fallen in love with.

Atrus has no hope - the world is decaying too fast, and the only way to save it would be to rewrite certain passages in the linking book that maintains the world. Since the entire purpose of going to Riven in the first place was to trap Gehn into an Age he couldn't write his way out of, Atrus cannot allow Gehn to recover the only linking book out of the Age - Atrus' linking book to Myst.

And so, Atrus stands over the Star Fissure, holding the book out - so that when he links through, the book will plunge into the abyss and be lost forever. He links, the book falls into the Fissure, and everything SEEMS to be going according to plan...

Unfortunately, when he links back to Myst Island, Sirrus and Achenar are waiting. They trap him in the book that links back to the D'Ni caverns, tearing the page out of the white book. Unfortunately, they then fall into traps HE set for anyone who might intrude on the island, as they link into the red and blue books.

SOMEHOW, the Star Fissure is linked to our world - no one really understands quite how in the game. But, as the linking book to Myst falls through the Fissure, it eventually shows up on Earth - where it is found by "the Stranger" (the player). The Stranger, knowing nothing of linking books, links through to Myst... and the first game begins.

At the end of the first game, Atrus is freed, the trap books holding Sirrus and Achenar are destroyed (BUT, the Ages they are trapped in are NOT destroyed - this leads us to the plot of Myst IV: Revelation), and Atrus asks his new friend the Stranger to go to Riven, rescue Catherine, and trap Gehn while Atrus writes the necessary lines into the linking book to stabilize Riven as long as he can...

At the end of Riven, Gehn has been trapped in the book Atrus wrote for him, Catherine is freed, and by breaking the cover over the Star Fissure, you summon Atrus. When he arrives, he takes Catherine and the trapped book back with him, leaving the rapidly disintegrating Age.

Which leaves the Stranger to jump into the very Fissure which once brought the linking book to him. Since the book made it safely to the Stranger's world, Atrus hypothesizes that it can take the Stranger home as well...

Which leaves the player right back where they started - with a linking book that bridges to Myst in his hands...

Events in later games seem to imply that not only does the Stranger occasionally use the linking book to visit Atrus, but that Atrus has either written a linking book to return him to Earth, or another means has been found to do so.

Nicely explained =D

~×They can have the wOrld,, I'll create my Own×~ kisses, your boy(F)