I had a mad ambient buying period in the mid-90s and then tended to play more active Progressive music, only occasionally re-visiting the ambient albums.  I'd been lent ambient albums in the meantime but rarely had they made much impact.  I was lent this one and was so impressed that I had to buy it.  Looking around on the internet, it has been very well received.
Murcof is the working name of Mexican Fernando Corona, and Martes is his first album under this pseudonym.  I suppose this music does fall into the ambient category although at times there's a fair bit going on.  It features beautifully recorded real instruments such as piano and cello processed and blended with other weird sounds, usually with some sort of beat applied over the top.  The way that the beat is superimposed over the top may cause annoyance in some cases as at times the two parts of the music seem to have little or no relationship with each other.  This is especially true on the first track Memoria and it might put some people off.  I don't actually mind it, but for those of you that find it tricky you should persevere.  This becomes less of an issue as the album progresses although some of the latter tracks are more beat-driven than ambient. 
It's worth listening to this album on a good hi-fi system and you should also try headphones.  Murcof has added a lot of subtle detail under the main music with tiny bleeps and fuzzes that can be easily overlooked on a casual listen.  Other tricks he tries are to put in backward sections and to literally cut the music up so that it's playing away and then you are jarred out or your trance as short sections are removed momentarily.  This all helps to make the thing sound interesting and not just a constant lush sound from start to finish.
One standout track is Mir for its sheer perfection of what Murcof is trying to do - the way that a repeated harsh-sounding jazz piano chord is juxtaposed with strings, a beat and some gorgeous gentle piano chords.  Another is Muim, as a bleepy start gets a low beat and becomes a harmonious male choir and female solo voice.  The timing of the beat is then played around with in an exquisite way.
To sum up then, an excellent ambient/electronic album that stands repeated listening.  It has a warmth and human touch that avoids the robotic and cold repetitiveness of a lot of music.  Also it has far more depth than your average 'chillout' album that immediately sounds nice on the surface but doesn't reveal anything below that.  It's one of a kind and as such I wouldn't want a Martes II - I'm perfectly happy with this one.  It's made me listen to ambient/electronic music again and has re-awakened my interest in this sort of music.  My only criticism is that it does seem to be a bit of a one-trick album; he's come up with an excellent sound and uses it on all of the tracks.  I guess I'm comparing it with people like Future Sound of London who would do this for one or two tracks and then do totally different stuff on the rest.