 To finance his pursuits, he began The Book Collector's Service Bureau, a mail-order book service, beginning with a letter of introduction sent to 100 homes.The venture proved so successful that for a time Marcus considered entering that line of work full time, concerned that entering the retail business might curtail his freedom of expression in politics and other areas of interest; his father persuaded him that he would always be granted the liberty of his own views, and pointed out that retailing was more profitable and thus would allow him to amass a large book collection that much sooner.After receiving a B.A.