In 1831 he started 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."
The name of Bohn is principally remembered by the important Libraries which he inaugurated: these were begun in 1846 and comprised editions of standard works and translations, dealing with history, science, classics, theology and archaeology, consisting in all of 766 volumes. One of Bohn's most useful and laborious undertakings was his revision (6 vols. 1864) of The Bibliographer's Manual of English Literature (1834) of WT Lowndes. The plan includes bibliographical and critical notices, particulars of prices, etc., and a considerable addition to the original work.
It had been one of Bohn's ambitions to found a great publishing house, but, finding that his sons had no taste for the trade, he sold the Libraries in 1864 to Messrs. Bell and Daldy, afterwards G. Bell & Sons. Bohn was a man of wide culture and many interests. He himself made considerable contributions to his Libraries: he collected pictures, china and ivories, and was a famous rose-grower. He died at Twickenham on the 22nd of August 1884.