This post was contributed by Jason Ramsay-Brown and Haldeman-Julius.org. Take a moment to visit their site, it’s quite nicely put together.
—— About EHJ and the Little Blue Books ——
Emanuel Julius was born in Philadelphia on July 30, 1889, the third of six children. He was an ardent advocate of socialism throughout his formative years, in time taking employment in the ranks of America’s growing left-wing media. His passions eventually brought him to Girard, Kansas, the epicenter of the nation’s socialist press, to work for the infamous “Appeal to Reason” newspaper. It was here he became romantically involved with Marcet Haldeman, granddaughter of Senator John H. Addams, and niece of Nobel Peace Prize winner, Jane Addams. The two were wed on June 1st, 1916 and mutually assumed the surname Haldeman-Julius.
wonderful little books by Emanuel and Marcet Haldeman-Julius
In 1919, Emanuel and Marcet Haldeman-Julius purchased controlling interest in the Appeal to Reason. As his first act as owner, Emanuel ordained the publication of a “University in Print” - a library of classic literature, social discourse, and political rhetoric aimed at being attractive and affordable to the average working person. These 3½ × 5 inch volumes were designed to fit in a worker’s back pocket, and printed with the cheapest materials possible in order to keep costs low. The initial booklets, known as “The Appeal’s Pocket Series” were priced at 25 cents a copy, and available only by mail order. Over the next few years, however, the series would change names several times, and as distribution escaped the restraints of mail order, prices would plunge as low as 5 cents a piece.
In 1923 the publication would become known as the Little Blue Book series, a name that would last until its final days some five decades later. Staunch left-wing tracts like #4 “Soviet Constitution” and #5 “Socialism vs. Anarchism” soon found themselves accompanied by volumes like #1013 “The Best Irish Jokes”, and #1111 “Prostitution in the Medieval World”. By 1978, when the press & warehouse were destroyed by fire, some 2000 titles would have been issued, and hundreds of millions of booklets sold.
—— About Haldeman-Julius.org —— 
Haldeman-Julius.org site is devoted to the history, identification and collecting of the various 3½ × 5 inch volumes published by Emanuel Haldeman-Julius (and his son) from 1919 to 1978. These series include: The Appeal’s Pocket Series, People’s Pocket Series, Appeal Pocket Series, Ten Cent Pocket Series, Five Cent Pocket Series, Pocket Series, and the most popular and prolific series title, the Little Blue Book.