Does anyone know if the tracks are in chronological order? Like Vol 1 is the first half of the season and Vol 2 is the second half i.e.?
No, it's more by style/mood. The first volume is all Daniel Pemberton material and mostly pure orchestral. For those that really just want a shorter sampling of the most accessible score music, it might be sufficient. The second volume adds the Samuel Sim material (in addition to more from Pemberton) and it contains more of the atmospheric parts of the score, including the synth and more folk music style pieces, although there is still a lot of orchestral material there too.
The new issue of FSM has reviews of both volumes and give a pretty good overview.