Joseph Smith and the Book of Mormon is about Martin Harris, the missing pages, and how this mistake has been solved.
Martin Harris was the first scribe for Joseph Smith in translating the Nephite records. This process would work by Joseph reading, translating and then speaking the words on the plates to Martin who would then write the translated record down on paper.
Before I continue on to the missing pages of transcript I will explain something concerning the Book of Mormon. The Book of Mormon, as you may or may not know, is actually a collection of fourteen books written by many prophets, as well as a small section called Words of Mormon that explains somewhat the make-up of these books. The last prophet of the Nephites, Mormon, along with his son Moroni, went through all the records kept by the prophets and kings and chose fifteen to include in the abridged set of plates that were given to Joseph Smith.
You may have noticed that I said that Mormon and Moroni included fifteen books and the Book of Mormon is only fourteen. This missing fifteenth is what is referred to as "the missing 116 pages."
In 1827 Joseph and Martin began work on translating and in the following year they completed the first book, the Book of Lehi, 116 pages long. Joseph and those that believed in the gospel he taught had been persecuted and ridiculed for that entire year. Martin was not exempt from this treatment and desired to take these finished pages back to his town to show his wife and friends that they were doing a real work. He asked Joseph if he would pray to the Lord and ask if the pages could be taken home. The answer was no. Mr. Harris, however, asked if Joseph would pray again, and the answer was again no. Determined to take these pages to show his wife and friends he plead that Joseph would ask again.
Martin eventually took the finished 116 pages with him. When the time came that Joseph asked for them back they could not be found. Someone had taken the pages and they could therefore not be returned to the Prophet. At realizing this Joseph went to the Lord concerning the matter who took away the gift of translation, as well as took back the plates and interpreters, until the young Smith had proved his trust in the Lord.
Eventually the time came that Joseph Smith received the ancient records, interpreters and gift of translation again. This time Martin Harris was not allowed to work as scribe. Working in Mr. Harris' place was Oliver Cowdery. They finished the work of translating the records but did not ever re-translate the Book of Lehi.
More on Joseph Smith and the Missing Pages:
116 Missing Pages
Revelation Concerning Joseph and Martin Harris Losing the Transcript:
Doctrine and Covenants, Section 3 and Section 10
Translating the Plates