If you're only going to read one definitive book about Caravaggio, then I guess it has to be Andrew Graham Dixon's 'Caravaggio: A Life Sacred and Profane'.
I enjoy Andrew Graham' Dixon's obvious passion for his subject, whether he's presenting on television, or in his writing.
It's well-researched, well-written, and scholarly without being dry. It is informative about the paintings, the person and the times in which the artist lived, which help to contextualise and explain the dark aspects and contrasts of Carvaggio's personality and his art, which are inextricably intertwined. It's a painstaking piece of research which forms an authoratative account of a larger-than-life, bigger-than-death character. and functions both as a definitive piece of art historical research and also as a really good read.
(My only quibble is that the indexing isn't great, and there is a lack of cross-referencing between text and illustrations, but I guess that wasn't Mr Graham Dixon's department.)
For another aspect of Caravaggio, there's this book - 'Painting for Profit; The Economic Lives of Seventeenth Century Italian Painters' by Richard E Spear and Philip Sohm.
This is the nitty-gritty of business and accountancy deflating the loftiness of art, as a group of art historians and economic and social historians get out their calculators and tape measures, apply them to the works of the Baroque Italian masters, including Carvaggio and his contemporaries, rifle through their expense accounts and get down to brass tacks with an audible ka-ching.
Thus we have the cost per square metre and per figure of various Italian altarpices, such as Caravaggio's Calling of St Matthew in S Luigi dei Francesi in Rome - at 322cm x 340cm, it cost 200 scudi in total; 18 scudi per square metre, and 27 scudi per figure. Domenichino's Life of St Cecilia in the same church 10 years later commanded only 8.5 scudi per square metre and 10 per figure. Those are the figures, but what does that say about the comparable 'worth' or value of each piece of art? How do you actually value art, its skill, its emotional power, its message? Can a piece of art be worth more to one person than other? Is one person's art not actually art at all to another person?
TThese aren't questions covered in this book. With its tables of figures, details of the economics and politics of commissions, inter-studio rivalries and the basic necessity for artists to run a business and make a crust, it's a sobering and dry counterpoint to the creative process. Behind the aesthetics, the beauty and the ideas, there is the reckoning.
Art may be big business today - take a look at a book such as Seven Days in the Art World by Sarah Thornton...
...but art as an economic commodity certainly isn't a modern idea at all.