Can you recommend some books about Caravaggio?

Walter Friedlaender, Caravaggio Studies
Andrew Graham-Dixon, A Life Sacred and Profane
Howard Hibbard, Caravaggio
Helen Langdon, Caravaggio: A Life
Francine Prose, Caravaggio: Painter of Miracles
Catherine Puglisi, Caravaggio
Peter Robb, M: The Man Who Became Caravaggio
Keith Sciberras & David Stone,  Caravaggio and the Knights of Malta
John Varriano, Caravaggio: The Art of Realism
Genevieve Warwick (ed.), Caravaggio: realism, rebellion, reception

The following are journal articles or part of anthologies:

Joseph F. Chorpenning, Another Look at Caravaggio & Religion (Artibus et Historiae)
Philip Sohm, Caravaggio’s Deaths (Art Bulletin)
John Varriano, Caravaggio & Violence (Storia dell’Arte)
John Varriano, Caravaggio & Religion (from Saints and Sinners edited by Franco Mormando)

Much more about Caravaggio exists in print. Caravaggio.com has a wonderful and extensive list of scholars have worked on Caravaggio, along with citations of their respective works.