Below is a a very condensed summary of the Book of Mormon:
1 Nephi: An Israelite family, Lehi and Sariah with their children Laman, Lemuel, Nephi, Sam flee Jerusalem due to a vision Lehi had regarding the pending destruction of Jerusalem at the hands of the Babylonians. Shortly after fleeing, the sons return twice, first for the sacred texts as found upon the Brass plates and second to convince another family, the family of Ishmael, to join them on a trip to the promised Land (the Americas). Lehi and Sariah have two more children during their journey, Jacob and Joseph.
2 Nephi: The family breaks apart with the righteous following Nephi and the wicked following Laman and Lemuel. Nephi teaches his family from the sacred scriptures, primarily the words of Isaiah. He also teaches doctrine on baptism, and reveals that the name of the Messiah is Jesus Christ.
Jacob: Nephi’s younger brother Jacob becomes the prophet/leader and exhorts the people to righteousness. He condemns polygamy and teaches the allegory of the vineyard/olive tree. He contends with an anti-Christ name Sherem.
Enos: Jacob’s son prays in the woods for forgiveness of sins and is granted a spiritual manifestation of redemption by the atonement of Jesus Christ. He is then given an assurance that the Nephite record would be revealed to the Lamanites in the last days.
Jarom/Omni: Some wars and contentions and the fleeing of Nephites to the land of Zarahemla where they discover the people of Mulek. The people of Mulek fled Jerusalem right after the Babylonian invasion. Mosiah the king of the Nephites becomes the king of Mulekites as well.
Words of Mormon: Bridge between the plates of Nephi and the abridgement that Mormon was creating.
Mosiah: King Mosiah dies, has a son Benjamin who is king. Benjamin provides a last sermon at the temple, where he taught from a tower and the people fell down in amazement of their own nothingness. Benjamin reveals that the name of the Messiah is Jesus Christ. Benjamin’s son Mosiah becomes king. The story is interjected with the events of a splinter group led by Zeniff, who returned to the Land of Nephi. In the sub-story, a wicked king Noah kills a prophet named Abinidi, because he preached of Christ. A priest of Noah, Alma, believes in Abinidi and forms a church at the waters of Mormon. They eventually flee the land and join back up with the people of Zarahemla. The book ends with Mosiah establishing a quasi-republic administered by a complex system of lower and upper judges with a chief judge acting as the overall leader.
Alma: The son of Alma, Alma Jr. becomes the chief judge and prophet. Upon recognizing the wickedness of the people gives up being the chief judge and focuses on teaching the gospel. Meanwhile some of the sons of Mosiah also preach to the Lamanites and have incredible success. By mid-Alma, the wars between the Lamanites and the Nephites become the focus of the story.
Helaman: Helaman Jr., the son of Helaman, the son of Alma Jr. takes over as the Prophet and has two sons Lehi and Nephi. They preach repentance and the Lamanites and Nephites resume to wars. A Lamanite (Samuel) prophesies of Christ’s birth, death, and resurrection while miraculously avoiding injury from arrows being shot at him.
3 Nephi: An incredible manifestation of Christ’s birth which included the lack of darkness during the night. The Nephite civilization is busy with war, and secret combinations. The Nephite nation collapses into lawlessness as the chief judge is overthrown. Nephi Jr. the son of Nephi preaches and performs miracles including raising his brother from the dead. Christ’s crucifixion is manifested with massive upheaval and 3 days of darkness. Christ appears to the people at Bountiful where he teaches them about baptism and those who are blessed. Christ teaches them to create a Church after his name and quotes from the Old Testamant Malachi.
4 Nephi: Nearly 300 years of peace and prosperity for the Nephite nation as they follow the teachings of Christ. The people eventually forget Christ, and fall back into lawlessness and secret combinations.
Mormon: One of the final Nephite prophets, as a young 15 year old is visited by Jesus Christ. He is told by Ammoron, a prophet, that when he is roughly 24 years old he should take up the history of the Nephites, and compile The Book of Mormon. Later he becomes a great military leader of the Nephites, and sees some military success, but is discouraged by the wickedness of the people. Mormon eventually dies in battle and passes on the responsibility of maintaining the record to his son Moroni.
Ether: A separate story-line introduced by Moroni that comes from plates found by a band of Mulekites. The story includes a family whose leader was called Jared, and whose brother was the prophet and was referred to as brother of Jared. They escaped calamity at the Tower of Babel. They traveled to the ocean, via an eastwardly route. Upon arriving at the Ocean, the brother of Jared sees a vision of Christ who forgives his sins and redeems him from the fall. He touches 16 stones to provide light into 8 submarine like ships. They travel to the new world and are known as the Jaredites. They fight a lot, and have secret combinations which after about 2000 years destroy the entire civilization.
Moroni: After finishing the abridgement of the Jaredites, Moroni decides to explain how the sacramental prayers should be performed along with priesthood ordination. He also teaches that children under 8 shouldn’t be baptized and he defines what are spiritual gifts. He finishes by encouraging us to pray about The Book of Mormon to know if it’s true.