You'll quickly notice that we're working our way through the Gospel story backwards - that is, starting at the Ascension, heading through the resurrection and cross, past the stories in the middle of the narratives, and finally ending up with the birth of Jesus and the annunciation by Gabriel to Mary.
Why? Two main reasons.
The first is practical. It means we can finish the series by looking at the birth stories around Christmas. Which seems more appropriate than reading about the betrayal, trial, and crucifixion while we're singing carols ...!
The second is more creative. When we read a story forwards we usually interpret each event in light of all the past events. Going backwards allows us to ask a whole different set of questions. How do we understand the cross in the light of the resurrection? What does the last supper look like when the crucifixion is still fresh in our minds? How does the passion story color our reading of the transfiguration? And what does the Christmas story look like when we read it at the end of all the Gospel stories, rather than the beginning?
Think of it as a fresh angle on a familiar story.