I got curious browsing around Amazon a few weeks ago and wound up ordering a copy of View of the Hebrews by Ethan Smith. I'd read in a few places, including the CES Letter, that this book was evidence that the Book of Mormon was fictional to the point of plagiarism. I was kind of disappointed. I don't think that accusation really holds up.
There is a comparison chart attributed to B. H. Roberts in the CES Letter that delineates the similarities between these two early 19th century publications. It seems like a generally accurate chart, but there are a lot of points that aren't particularly damning. And some are too vague, like "settlers journey northward" and "religion a motivating factor." Settlers travel north all the time in history and in fiction and religion is a common factor in a lot of people's motivations. The Samuel the Lamanite connection is the most compelling, I believe, but even that is introduced very early and you're still left with more than a hundred pages of material that can be interpreted as having flimsy correlations to the Book of Mormon.
I don't think it's useful to adduce View of the Hebrews when arguing that the Book of Mormon is a fraud. I think it's very weak evidence. It fits the narrative that I believe since I've already concluded that the Book of Mormon is not scripture, but it's not strong enough to convince anyone who still follows the prophet. It's not definitive enough or conclusive enough. It's one of the arguments that FAIR pounced on most voraciously in their response to the CES Letter, and it's probably because they were excited to have something that could be dismissed with relatively little effort.
View of the Hebrews has one major evidence that may help convince a Mormon who's already begun questioning and researching, though. It pretty exhaustively indicates that the idea of Native Americans being descendants of ancient Jews was not new in the 19th century. It always seemed groundbreaking to me when I was a faithful church member because I grew up in an era in which a different origin for Native Americans was almost universally agreed upon as fact. But back in Joseph Smith's day, the Hebrew-Indian thing was a theory with some popularity. Fawn Brodie mentioned this in passing in No Man Knows My History, but Ethan Smith's book was written with the sole intent of proving that theory. He cited numerous other contemporary scholars and thinkers in support of his thesis. The existence of View of the Hebrews and the breadth of work it references to bolster its claims should at least take some of the shine off the Book of Mormon's mystique. But again, it only really points to Joseph Smith penning a fictional history if you're already leaning that direction. It seems easy to minimize or discredit if you still believe the truth claims of the LDS church. It's not the smoking gun of plagiarism it's sometimes depicted as.
It's a weird read, too. Very racist to a modern eye. It's very dry to a modern eye, too, as the prose hasn't aged well. But it's interesting nonetheless. The Late War is a totally different story. I couldn't stomach more than a few chapters of that before giving up.