
Their study (which excluded the Bible) found Late War to have a highest number of four word phrases in common with the Book of Mormon. The Johnsons used multiple algorithms to confirm their results and have requested peer review of their research.
The wide availability of old texts at various universities, archive.org and google.com have allowed "Big Data" studies to proceed. Details of their study are available here, with further explanation here. (Update: here is a new, detailed page).
An earlier comparison of Late War and the Book of Mormon was done by Rick Grunder, and can be read here. Grunder looks at similarities between the two texts including war between the wicked and righteous, maintaining the standard of liberty with righteousness, reports of battle causalities, righteous Indians vs savage Indians, false Indian prophets, the conversion of Indians, brass plates, the worthiness of Christopher Columbus, ships crossing the ocean, elephants/ mammoths in America, literary hebraisms, use of "it came to pass," "curious workmanship," "chief captains," and others.