Myst DS will not only contain the original four ages, Channelwood, Mechanical, Selentic and Stoneship, but also the Rime Age which was previously only seen in the under-exposed version called realMyst. Rime Age was originally meant to appear in the first version of the game, but production time and cost, as well as the sheer size of the game, prohibited it from appearing in the release. While Myst DS won't have the weather or 3D effects that realMyst had, besides the inclusion of the Rime Age and some added bonuses for being on the DS, this release is going to be a copy of the earliest version.
When I say the game tries to be as close to the original creation as possible, this means that the developers, Hoplite Research, did all they could to reproduce the original Myst experience, right down to the on-screen video and vocals along with a completely remastered soundtrack taken from the raw files created back when Myst first came out. In order to get the video onto the DS and not cause too much of a space problem, the development team had to come up with a proprietary compression algorithm.