Actually, it's garbage

According to The Urantia Book Fellowship (UBF), The Urantia Book (UB) is

an anthology of 196 'papers' indited [i.e., dictated] between 1928 and 1935 by superhuman personalities.... The humans into whose hands the papers were delivered are now deceased. The means by which the papers were materialized was unique and is unknown to any living person.

The UB Fellowship was founded in 1955 as the Urantia Brotherhood and is an association of people who say they have been inspired by the "transformative teachings" of the UB. According to the UBF, these "superhuman personalities" are from another world. They synthesized the work of more than 1,000 human authors in a variety of fields, including an "astronomical-cosmological organization of the universe" unknown to modern science and an elaborate extension (700 pages) on the life of Jesus. The UB also reveals that the "Universe is literally teeming with inhabited planets, evolving life, civilizations in various states of development, celestial spheres, and spirit personalities." In short, the UB is over 2,000 pages of "revelations" from superhuman beings which "correct" the errors and omissions of the Bible. "Urantia" is the name these alleged superhumans gave to our planet. According to these supermortal beings, Earth is the 606th planet in Satania which is in Norlatiadek which is in Nebadon which is in Orvonton which revolves around Havona, all of which revolves around the center of infinity where some sort of god dwells.

Others aren't so sure of the celestial origin of these writings. Matthew Block, for example, has identified hundreds of passages in the UB that are clearly based on human sources, but which are not given specific attribution. (Some might call this plagiarism, even though William Sadler (the main author) admits on page 1343 that he used many human sources. Others might say that since Sadler didn't lift passages word for word from the many sources he used, what he did isn't, strictly speaking, plagiarism.)

Martin Gardner is also skeptical of the UBF's claims. He believes the UB has very human authors. Originally, he says, the UB was the "Bible" of a cult of separatist Seventh Day Adventists, allegedly channeled by Wilfred Kellogg and edited by founder William Sadler, a Chicago psychiatrist, who is actually the author of most of the work (with the help of his son). According to Gardner, in addition to an array of bizarre claims about planets and names of angels and the like, the UB contains many Adventist doctrines. Sadler died in 1969 at the age of 94 but his spiritual group lives on. Sadler got his start working for Dr. John Harvey Kellogg, Adventist surgeon, health and diet author, and brother of cornflake king William Keith Kellogg. These are the same Kellogg brothers who were featured and lampooned in the movie "The Road to Wellville."

One can easily understand why Gardner suspects that the UB has human rather than superhuman origins. The book has all the traits of humanity upon it. For example, our human philosophers and theologians are mimicked perfectly in passages such as the following:

The philosophers of the universes postulate a Trinity of Trinities, an existential-experiential Trinity Infinite, but they are not able to envisage its personalization; possibly it would equivalate to the person of the Universal Father on the conceptual level of the I AM. But irrespective of all this, the original Paradise Trinity is potentially infinite since the Universal Father actually is infinite. (Foreword XII, The Trinities)

Any medieval casuist would be proud of such writing and thinking.

Primary supernaphim are the supernal servants of the Deities on the eternal Isle of Paradise. Never have they been known to depart from the paths of light and righteousness. The roll calls are complete; from eternity not one of this magnificent host has been lost. These high supernaphim are perfect beings, supreme in perfection, but they are not absonite, neither are they absolute. (Paper 27)

Some UBFers are attracted not so much to the theology, but to its great insights. Here are a few of those insights culled from paper 100, "Religion in Human Experience." Ask yourself if a superhuman being was necessary to reveal these gems.

The experience of dynamic religious living transforms the mediocre individual into a personality of idealistic power....

Give every developing child a chance to grow his own religious experience....

Religious experience is markedly influenced by physical health, inherited temperament, and social environment....

Spiritual development depends, first, on the maintenance of a living spiritual connection with true spiritual forces....

The goal of human self-realization should be spiritual, not material....

Human likes and dislikes do not determine good and evil; moral values do not grow out of wish fulfillment or emotional frustration....

Jesus was an unusually cheerful person, but he was not a blind and unreasoning optimist....

If the philosophical, theological or spiritual insights do not impress you, then you might want to consider the scientific insights of the UB, such as the resurrection of the pre-Adamite thesis of Isaac de la Peyrère (1596-1676), who felt compelled to believe that the Bible is the history of the Jews, not of all people, and that in order to explain things such as racial differences the most reasonable hypothesis is that races of people existed before Adam and Eve.

In addition to the claim that the UB was channeled by Wilfred Kellogg and the claim that it was written primarily by William Sadler, there is the claim of Ernest Moyer, who believes that the UB is a revelation from a god that appeared "out of thin air" in fully developed form, exactly as we know it today. Moyer claims that Sadler was put through a lengthy process by our "planetary supervisors" in order to prepare him to accept the UB as true revelations. The process began by introducing Sadler to the Sleeping Subject (SS), whose nocturnal ramblings would later be understood to be preparatory messages from extraterrestrial "midwayers." According to Moyer, "SS was a member of the Chicago Board of Trade, a highly pragmatic, hard-nosed business man who did not believe in 'psychic' phenomena or any such nonsense." Why SS was selected for this task is unknown, but Moyer assures us that the midwayers never took over SS's mind and came only at night when SS was unconscious so as not to disrupt his life too much. Moyer contrasts this with the evil spirit who invaded Edgar Cayce during the daytime, a sure sign that Cayce was a false prophet. Sadler was selected, according to Moyer, because of his personality and training. A more obvious analysis is that Sadler selected himself because he was the source of the SS material.

Moyer is convinced that we are on the verge of a nuclear holocaust and that the UB offers advice on how to save oneself from destruction and what to do afterward. This is all part of some god's plan, as revealed to Sadler. According to Moyer, "God [sic] is using this technique to screen the human race."

It seems to me that some god tried this once before with water instead of nuclear bombs. Well, if at first you don't succeed....