RuheBlut: Indeed =p I did like Myst 3 Exile as well the whole concept of differing eco systems and how they each had an energy source written into them such as the one volcanic age which name eludes me lol. Out of all the books though for the 3 Myst books The Book of Atrus was my favorite followed by the Book of D'ni the Book of Ti'anna was good but the beginning started out so slowly it took me a bit more to get into it.
The book of Atrus probably has the best writing of the 3, although i can't quite pick a favourite, they all adress aspects that managed to capture my imagination, but the topic of the Gartenay split into D'ni/Terahnee adressed in Book of D'ni is probably the one that interests me the most. I agree with you though, The Book of Ti'ana is a little bit too descriptive early on and takes a little while to pick up.
Exile being very focused, in terms of plot, on events that are mostly unrelated with the gerater story outlined by the other games in the series didn't impressed me that much in terms of story, but the Ages featured in it are beautiful and interesting. Who could ever forget that awesome ride in Amateria ? ;)