Short answers, pulled from the story.
Engels wrote the book during his stay in Salford and Manchester between 1842 and 1844, and the German original was published in 1845. An English translation appeared in New York in 1887 and in London in 1892.
Florence Kelley, an American, translated the book into English in 1885, working under her then-married name Florence Kelley Wischnewetzky. The translation was authorized by Engels, who wrote a new preface for the English editions.
Engels documented that in industrial cities such as Manchester and Liverpool, death rates stood at roughly 1 in 32 compared with a national average of 1 in 45 or 46. In Carlisle, child deaths before age five rose from 4,408 to 4,738 per 10,000 after mills were introduced, and adult deaths before age thirty-nine climbed from 1,006 to 1,261 per 10,000.
After their second meeting in 1844 in Paris, Marx read the book and was profoundly impressed by it. Engels used the book to convince Marx that the working class could be the agent and instrument of the final revolution in history.
Engels was twenty-four years old when he wrote the book, a fact he acknowledged in his 1892 preface, noting that the work bears the stamp of his youth.
In his 1892 preface, Engels wrote that repeated epidemics of cholera, typhus, and smallpox had forced British cities to improve sanitation, and that the most crying abuses described in the book had either disappeared or been made less conspicuous. He argued, however, that France, Germany, and especially America had by then reached a similar stage of industrial development to England in 1844.