Traditionally the author is Luke, a physician and traveling companion of Paul, but the evidence is not convincing either for or against. It is, however, pretty much agreed the same author wrote both Luke and Acts.
Luke has the virgin birth, but the nativity he tells is quite unlike that of Matthew, and the census puts it about six years later!
In Luke we see an elaboration of the Jerusalem appearances, after the very brief appearance in Matthew. He was writing sufficiently long after the event that such stories could start to circulate in the community without the people who were actually there refuting it. Luke diligently recorded these fabricated stories for his patron.
Galilean Appearances?Indeed, there is no mention of Jesus appearing in Galilee,
Why are the Galilean appearances absent? We have no way to know. There might have been some political reason, and Luke wanted to play down Peter's role in the events. For whatever reason, the events in Galilee - the real sightings - get reduced to an off-hand comment that Jesus has appeared to Peter buried in the Emmaus account:
Luke 24:33 They got up and returned at once to Jerusalem. There they found the Eleven and those with them, assembled together 34 and saying, “It is true! The Lord has risen and has appeared to Simon.”
This is frankly bizarre. These two men saw Jesus, and Luke goes into detail about how it happened, but the first thing they say is how Jesus appeared to someone else, and event Luke chose to omit!
Nature of the ResurrectionBy this time the concept of the resurrection had changed. There is no suggestion in Luke that Jesus was just the prototype as Paul had believed - perhaps because by now claims that the apocalypse was here were growing stale.
No longer was Jesus resurrected in a new body shining bright as a star. Now the resurrection is Jesus in his original body, and Jesus is at pains to establish he is not a ghost - undoubtedly to counter the claims of Christianity's opponents.
Luke 24:37 They were startled and frightened, thinking they saw a ghost. 38 He said to them, “Why are you troubled, and why do doubts rise in your minds? 39 Look at my hands and my feet. It is I myself! Touch me and see; a ghost does not have flesh and bones, as you see I have.”
The AscensionWhile the Galilean appearances are missing, we do get the Ascension for the first time. This may have been inspired by Elijah being taken up to heaven (2 Kings 2).
It is curious that in Luke it reads as though the Ascension happened later in the day that Jesus was resurrected, but Acts has them forty days apart. Given they had the same author, this illustrates how the author was happy to modify the story to make a good narrative, and was less concerned with being historically accurate.
Blame the JewsAs a gentile, the author of Luke shifts all the blame for Jesus death squarely on the Jews.
Luke 23:13 Pilate called together the chief priests, the rulers and the people, 14 and said to them, “You brought me this man as one who was inciting the people to rebellion. I have examined him in your presence and have found no basis for your charges against him. 15 Neither has Herod, for he sent him back to us; as you can see, he has done nothing to deserve death. 16 Therefore, I will punish him and then release him.”  [a]The reality is that Pilate was cruel and ruthless, and had far more reason to crucify Jesus as a rebel leader than the Jews did. But Luke was trying to sell Christianity to the Romans, so it was expedient to twist the truth.
18 But the whole crowd shouted, “Away with this man! Release Barabbas to us!” 19 (Barabbas had been thrown into prison for an insurrection in the city, and for murder.)
20 Wanting to release Jesus, Pilate appealed to them again. 21 But they kept shouting, “Crucify him! Crucify him!”
22 For the third time he spoke to them: “Why? What crime has this man committed? I have found in him no grounds for the death penalty. Therefore I will have him punished and then release him.”
23 But with loud shouts they insistently demanded that he be crucified, and their shouts prevailed. 24 So Pilate decided to grant their demand.
Sadly this has led to a strong anti-Semitic current in Christianity which culminated in the Holocaust, by way of numerous pogroms. It is worrying how the movie "The Passion of Christ" has so embraced this lie.