Sentence:  The extent of the business done in this line is not understood by those who have not looked into it. In New York there are 50 pool rooms and 500 <WSD>handbooks</WSD>; in East St. Louis, 20 <WSD>handbooks</WSD>; in Chicago, 5 pool rooms and 200 <WSD>handbooks</WSD>; ... 
Meaning of the word marked with <WSD> tags:  A place where illicit bets can be placed.