Bohn was born in London. He was the son of a German bookbinder who had settled in England. In 1831 he began his career as a dealer in rare books and remainders. In 1841 he issued his ""Guinea" Catalogue" of books, a monumental work containing 23,208 items. Bohn was noted for his book auction sales: one held in 1848 lasted four days, the catalogue comprising twenty folio pages. Printed on this catalogue was the information: "Dinner at 2 o'clock, dessert at 4, tea at 5, and supper at 10."