The book begins with a fifty-page essay on the development of jewellery design since 1900, which focuses on Europe (especially Italy; it was published in Italian as Gioielli Del Novocento) and America, though also briefly mentions Russia and Japan. Cappellieri cites the pave secret, serti mysterieux technique of Van Cleef & Arpels as "one of the most important innovations in the history of twentieth-century jewellery".
Cappellieri also discusses "the transitions between jewellery and the arts: design, architecture and fashion". This cultural context is sometimes excessive (for example, a full-page reproduction of a Giacomo Balla painting "that beautifully sums up the period between 1929 and the end of the Second World War. On 24 October 1929, which was a Thursday, the Dow Jones index crashed...").
Nevertheless, Twentieth-Century Jewellery is a comprehensive survey of modern jewellery, featuring jewels from a wider range of sources than other books on the subject. H Clifford Smith wrote Jewellery, the first comprehensive jewellery history, in 1908. A History Of Jewellery 1100-1870 (Joan Evans, 1953) is the other standard work. Modern Jewellery: An International Survey 1890-1963 (Graham Hughes, 1963) was the first guide to modern jewellery design. 7,000 Years Of Jewellery (Hugh Tait, 1986) is the most comprehensive international history of jewellery.