For those not familiar with The Urantia Book, it was first published in 1955. It is about 2,000 pages, covering the nature of the superuniverses and our local universe, the history of Urantia (our planet Earth), the role of the angels and rebel angels over the past 500,000 years, and the life of Jesus. It is quite dense, but also fairly readable.
An easier read is the series of books by Timothy Wyllie regarding his own life from the perspective of a rebel angel, which also includes a lot of information from The Urantia Book. I found these books both interesting and entertaining. Some of it may seem far-fetched, and yet it all makes a certain sense.