When it comes to figuring out how long it takes to read any document, it's a simple matter of mathematics. Take the length of the text in words, divide by the number of words a reader can be expected to read in a minute, and express the results in terms of minutes, days, years, etc. Of course, pure mathematics doesn't account for human frailties, such as the need to take a break or reread a portion they didn't understand, but for now, we'll put that aside.
According to Reading Length, the English translation of the Book of Mormon is 270,280 words. Assuming that the average adult — reading in English — can read 250 words per minute, then the Book of Mormon can be knocked out in just about 18 hours if read straight through. Of course, that would be physically impossible for most readers, so if it was undertaken in, say, eight-hour shifts, then the entire book could be completed in a little over three days.
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