Mormons often point to the length of the Book of Mormon and claim that no man could have written it without God's help. In particular, they say that Joseph Smith's lack of formal education meant he couldn't write such a book. There are several reasons why this is not a valid supportive argument.
1) Formal education — of which Joseph Smith had about three years — does not equal writing ability. Abraham Lincoln, one of Smith's contemporaries, had only a little over a year of formal education and yet he was able to speak, write, and debate masterfully. Like Smith, he was self-taught and also learned from others.
2) Today's Book of Mormon seems grammatically correct — but only because it underwent over 4000 changes to make it so. Read some of Joseph Smith's unedited writings from the 1830's. It is rambling, run-on and as unpolished as the first drafts of the Book of Mormon. In other words, God's supposed direct supervision of this work didn't set it apart from his other writings.
3) I'm a writer. If I didn't have to take care of household duties and social responsibilities, I guarantee you I could turn out longer works than the Book of Mormon, in less time than Joseph Smith took, and without copying wholesale sections from the book of Isaiah in the Bible. (I realize I've been writing all my life, but I could have done the same at age 22.)
For more information, see The Mormon Mirage 3rd Edition: A Former Member Looks at the Mormon Church Today (Zondervan, 2009). Also available as an audiobook and as an expanded-text E-book for Nook, Kindle and other reading devices.