I didn't care much for Lawson's preface and the editorial job is sometimes idiosyncratic -- (no, don't change the writer's word and then put the original word in the footnote. Leave the text alone, and explain the oddball term in the footnote!) -- but I can still appreciate the work he put in to the text. Especially using census data and other sources to identify some of the writers (who generally used initials rather than their full names)
The letters themselves range a lot in quality. You can see that Angry Internet Atheist Guy was alive and well in 1903. Others are more well thought out and very modern-sounding.
And there are certainly the occasional crackpots, starting with letter #1 from Franklin Heald of Los Angeles, CA:
"I can see no place in nature for any power except the expanding and contracting of matter by heat and cold. There is absolutely no motion or phenomena of nature made in any other way, and I make this assertion boldly and confidently, having had $1,000 on depost for about two years, which I offer to any person showing or proving any motion made in any other way." He then explains how the heat of the sun expanded matter, which then cooled and contracted into the planets, which slowly contract their way until they are absorbed by the sun.
Perhaps the most interesting thing is the demographics of the letters. The combo of progressivism, prohibition and women's suffrage maybe skewed the readership of the B-G B toward women and rural areas. Heck, the newspaper was published in Kentucky. But it's impressive how many of these letters come from what we'd now think of as red states, and how many are written by women. And, of course, the intersection of those two groups -- pioneer women in the Oklahoma Territory, and so on. A couple correspondents speak of dress reform: "Take off your corsets; put on a sensible shoe, plenty large; Wear no trained skirts and no heavy hats."
It's just not the case, as one angry San Francisco correspondent memorably opines, that "Today, nobody believes in a personal God but women, niggers, and lunatics."
Perhaps the monoculture of America was more potent back then, but it's a little sad how many of the essays should really be titled (like Bertie Russel's book) "Why I am not a Christian". But many are more cosmopolitan in their outlook, and a few even take the other readers to task for their focus on one religion. The miraculous conception of Jesus comes in for a lot of delicately phrased ridicule. A number of people opine that Yahweh was no gentleman... getting another man's wife in the family way, and all.
The idea that science and religion are opposites is also in full view in many of the letters. Of course, White's _History of the Warfare of Science with Theology in Christendom_ also stems from this time period. But as a detail, it's interesting looking back at this time, before the expansion of the universe had been discovered and Big Bang cosmology developed (and before radioactivity was well understood). There's a lot of "Atoms are eternal; the universe is eternal; no need for the god hypothesis."
Also many doctors, Civil War vets and Civil War doctors among the authors.
Lots and lots of mentions of Ingersoll and somewhat fewer of Tom Paine.
All in all, an interesting little time capsule of American Atheism from the turn of the previous century.