Theological differences between Mormonism and mainline Christianity tend to focus on faith versus works and the principle of "eternal progression," often to the exclusion of everything else. But the differing accounts of the "Fall of Man" are equally compelling and profound.
Mormons turn out to be in good company here. This first excerpt is from Moses 5:11, Joseph Smith's reinterpretation of Genesis (Eve is speaking):
Were it not for our transgression we never should have had seed, and never should have known good and evil, and the joy of our redemption, and the eternal life which God giveth unto all the obedient.
Compare that passage with Paradise Lost, Book 12 (Adam is speaking):
O goodness infinite, goodness immense!
That all this good of evil shall produce,
And evil turn to good; more wonderful
Then that which by creation first brought forth
Light out of darkness!
In both cases, rather than slinking out of the Garden of Eden, Adam and Eve see the upside of events. The most succinct summation of this interpretation is found in the Book of Mormon, 2 Nephi 2:25: "Adam fell that men might be; and men are, that they might have joy."
Incidentally, this point of view is also shared by Philip Pullman in his reinterpretation of Paradise Lost, "His Dark Materials."
A more traditional bone of contention is the question of salvation itself. Joseph Smith essentially attempted to split the theological differences. His answer to question "Are we saved by faith or works?" was "Yes." This compromise is clearly articulated in 2 Nephi 25:23:
For we labor diligently to write, to persuade our children, and also our brethren, to believe in Christ, and to be reconciled to God; for we know that it is by grace that we are saved, after all we can do.
Like debates over the Second Amendment, a great deal of theological weight rides on that last comma: whether we are saved only after all we can do, or whether we are saved by grace despite all we can do. "Orthodox" Mormons argue the former. "Neo-orthodox" Mormons argue the latter.
I'm inclined to believe that when Joseph Smith wrote this passage, he was operating more in the Protestant, "neo-orthodox" view. But later in his life, he would come to preach a far more works-based theology based on infinite but conditional grace that I term "neo-Pelagianism."
Mormon General Authority James Faust comes to the same conclusion, stating in reference to the verse in 2 Nephi:
Many people think they need only confess that Jesus is the Christ and then they are saved by grace alone. We cannot be saved by grace alone, "for we know that it is by grace that we are saved, after all we can do."
Which in some respects differs not greatly from Milton's peculiar brand of Puritanism (Book 11):
Given thee of Grace, wherein thou may repent,
And one bad act with many deeds well done
May'st cover: well may then thy Lord appeased
Redeem thee quite from Death's rapacious claim
Or as the necessity of mortality is spelled out in Alma 12:24 (which Jennifer paraphrases in chapter 37):
[T]herefore this life became a probationary state; a time to prepare to meet God; a time to prepare for that endless state which has been spoken of by us, which is after the resurrection of the dead.
So Adam and Eve are "sent forth, though sorrowing, yet in peace." We are works in eternal progress, infused with the hope that one day we may get it right. It is a theology that would seem to place salvation forever out of reach of mortal man. But as it turns out, God gives grades for effort.
As Joseph Smith famously preached in the King Follet Sermon, the most difficult of God's kingdoms to get into is Hell. The 18th century Swedish theologian Emanuel Swedenborg would have concurred: "All people who live good lives, no matter what their religion, have a place in Heaven."
However, once cast into the depths, "Free, and to none accountable, preferring / Hard liberty before the easy yoke" (Book 2), it is the most difficult to get out of.