The Urantia Book is a collection of channeled writings mostly from the 1930s, compiled and published in 1955.
No, it's not channeled, Dave. What is the source of your information? Surely you didn't write it yourself. Nor did you read the book, right? You're bearing false witness against God's new revelation to our world and you haven't even read the book! What's the difference between you and the guy who said this: He hath a devil, and is mad; why hear ye him?" (John 10:20)
The writings combine Christianity and an alleged history of the work and teachings of Jesus with a cosmology of extraterrestrial spirit beings.
No it doesn't, Dave. And "extraterrestrial spirit beings" are commonly called "angels." Isn't that what they're called in your religion, Dave? That's what they're called in our religion too. But "extraterrestrial spirit beings" sounds much more sinister, doesn't it? Dave? Be honest now.
The book presents an elaborate pseudo-history of the universe
No it doesn't Dave. Elaborate, maybe, "pseudo," not.
(the book actually claims there are many universes, super-universes, and so on),
Not exactly Dave. It just uses the word "universe" differently from the common usage.
and that the name of planet Earth in this cosmology is "Urantia".
That's good, Dave. Finally, something right.
The portion on the life of Jesus remains fairly true to the Bible stories of his life and teachings, except that in the Urantia Book Jesus was the most important spirit being in this universe who came to "Urantia" (Earth) to solidify his superior status, and the ideas of original sin or any need for Jesus to atone for human sins are rejected. In this, it departs from most Christian theology.
The Urantia Book is not based on "the Bible stories." The reason they are similar is the same reason two versions of a train wreck story are necessarily similar if not the same. The train wreck happened.
Nor does it matter if it "departs from most Christian theology." Some Christian theology is wrong, Dave. God is not a Christian, Dave, and Jesus was not The First Christian. And Jesus did not come to "solidify his superior status." Where did you get that from, Dave? Jesus came here primarily to "bear witness unto the truth" Dave, just like the bible says. (John 18:37) The Urantia Book says exactly the same thing, Dave.
A new age book.
What does that even mean, Dave? "A new age book" What does that mean, Dave? Apparently it's supposed to be derogatory, right? There was some need to say something derogatory at that point and someone said, "Hey, I know, let's say it's "a new age book," and call their angels, "extraterrestrial spirit beings." Yah, that'll fix 'em.