When will the Mormon Church Come Clean about the Book of Abraham?
Here are the sources for this information, they're quite detailed so I've done my best to give a high-level summary on this topic.
if you want a really technical explanation of the text there's a great summary here:
The Book of Abraham was derived from an ancient hieroglyphic document that Joseph Smith translated in 1835-1842 that was supposedly the personal work of the Biblical Abraham while in Egypt.
"In this book, Jehovah reveals to Abraham the nature of the universe and the order of all things, in a personal conversation, including knowledge of the planet Kolob, which is close to where God lives." - Translation and Historicity of the Book of Abraham - LDS.org
The LDS church has in its possession today, the original Egyptian papyri that Joseph Smith received his revelation and translated this document. I don't believe that anyone is challenging the authenticity of the document itself, only the true and accurate translation of the ancient Egyptian text.
The discovery of the Rosetta Stone in 1799 has steadily brought clarity and scholarly knowledge of Egyptian hieroglyphics, but at the time not a lot was known about the language. But that is not true today, Egyptian is no longer a lost language. Hieroglyphics, hieratic, and demotic scripts can and are translated today in the world's major universities.
The LDS church willingly asserts that:
"The Lord did not require Joseph Smith to have knowledge of Egyptian. By the gift and power of God, Joseph received knowledge about the life and teachings of Abraham" - Translation and Historicity of the Book of Abraham - LDS.org
I agree, however it does require that God has knowledge of Egyptian and it requires that Joseph Smith heard from God.
So how does Joseph's translation stand up?
According to numerous experts in their field, the text actually describes "The Breathing Permit of Hor". This is burial customs and instructions used by Egyptians, which is probably why it was with the mummies to begin with.
"The papyri were merely unremarkable burial trappings, quite likely from Antonio Lebolo's original mummies. They had nothing remotely to do with Abraham, the planet Kolob, or anything else found in Joseph Smith's translation. .... Smith's own callouts and identifications bear no resemblance to the actual contents. Ferguson said, "I must conclude that Joseph Smith had not the remotest skill in things Egyptian-hieroglyphics."
Another interesting part of this investigation is that the document is dated to about the 1st Century BC. This is about 1500 years after Abraham was historically established as being in Egypt.
Joseph Smith has reportedly said about his translation:
"This...was written by the hand of Abraham and means so and so. If anyone denies it, let him prove the contrary. I say it."
The LDS Church has taken the official position that:
"the Book of Abraham is that it is 'evidence of the inspired calling of the Prophet Joseph Smith' ".
There is no rational argument to support this claim, which means there no reason to believe what Joseph Smith has "translated" on this subject. The book of Abraham is a major pillar of Mormon beliefs, but if you can't rely on it what else is unreliable?
Is the Law of Eternal Progression untrue as well? what about Heavenly Father and the ultimate goal of a Mormon to again his own "godhood" like him?
What if anything or everything Joseph Smith said is untrue?
The LDS Church concludes that won't be able to settle this matter through evidence only by "confirmation" of the spirit. The Bible does talk about "other" spirits you know.
"The veracity and value of the book of Abraham cannot be settled by scholarly debate concerning the book’s translation and historicity. The book’s status as scripture lies in the eternal truths it teaches and the powerful spirit it conveys. The book of Abraham imparts profound truths about the nature of God, His relationship to us as His children, and the purpose of this mortal life. The truth of the book of Abraham is ultimately found through careful study of its teachings, sincere prayer, and the confirmation of the Spirit." - Translation and Historicity of the Book of Abraham - LDS.org
A burning feeling of "trueness" in your bosom should not replace intellectual reason and critical thought. Why? Because God is a God of order and reason, and if He cannot stand up to honest (critical) examination, then he's not God. I'm not saying we need to know the depths of God or understand him fully, I believe that is impossible, but we should not be able to find such apparent contradictions.
If Joseph Smith speaks for God then his actions, testimony, and prophecies should stand the test of time...