If the Octave is the feast extended, aggrandized (to use my yesterday's word that I've decided I do like) during eight days, the two days after Easter are in a special way Easter itself continued. (This occurs after Pentecost, too, although I can't recall if the Tuesday is specially so characterised or not). The Mass is Introduxit vos Dominus; the livret is here.
The Mass ordinary is the Lux et origo, Kyrie I, with Credo III. I myself welcome the simple loveliness of the plainchant; the splendors of a great feast well-observed are wonderful but I cannot imagine dealing with all of it for days in a row.
The first lesson is Acts 10,37-43.
The Alleluia follows. The Gospel is Saint Luke's, 24,13-35, the disciples who meet the Lord on Easter Day travelling to Emmaus. Nos autem sperabámus, quia ipse esset redemptúrus Israël et nunc super hæc ómnia tértia dies est hódie, quod hæc facta sunt, we had hoped that he would work the redemption of Israel but it is today the third day since all this has been done.
And the Victimae paschali laudes.
The antiphona ad Offertorium.
And the antiphona ad Communionem.
And the Mass ends with the Last Gospel as usual, and the Regina caeli laetare, the seasonal Marian antiphon (without the verses).
Jesus junxit se discípulis suis in via, et ibat cum illis: óculi autem eórum tenebántur, ne eum agnóscerent: et increpávit eos, dicens: O stulti et tardi corde ad credéndum in his, quæ locúti sunt Prophétæ, allelúja.