Recent, modern biographies of Muḥammad by English-speaking scholars who can read the Arabic sources (and hopefully other relevant languages as well) are surprisingly scarce. Nonetheless, three short and highly readable introductory books by such scholars can be enthusiastically recommended:
Brown, Jonathan A. C. Muḥammad: A Very Short Introduction. Oxford: Oxford University Press, 2011.
Cook, Michael. Muhammad. Oxford: Oxford University Press, 1983.
Donner, Fred McGraw. Muḥammad and the Believers: At the Origins of Islam. Cambridge, Mass.: Harvard University Press, 2012.
Fortunately for English-speaking readers, the historical study of the evolution of the biographical traditions about Muḥammad, and especially the hadith, have made a more robust showing. Essential readings are:
Brown. Jonathan A. C. Ḥadīth: Muḥammad’s Legacy in the Medieval and Modern World. Oxford: Oneworld, 2009. (An introductory work that is head and shoulders above any of its predecessors.)
Crone, Patricia. Meccan Trade and the Rise of Islam. Princeton: Princeton University Press, 1987.
Horovitz, Josef. The Earliest Biographies of the Prophet and Their Authors, ed. Lawrence I. Conrad. SLAEI 11. Princeton: Darwin, 2002.
Juynboll, Gautier H. A. Encyclopedia of Canonical Ḥadīth. Leiden: Brill, 2007.
Motzki, Harald, ed. The Biography of Muhammad: The Issue of the Sources. Leiden: Brill, 2000.
Motzki, Harald, with Nicolet Boekhoff-van der Voort and Sean W. Anthony. Analysing Muslim Traditions: Studies in Legal, Exegetical and Maghāzī Ḥadīth. Leiden: Brill, 2010.
Powers, D. S. Muḥammad Is Not the Father of Any of Your Men: The Making of the Last Prophet. Philadelphia, PA: University of Pennsylvania Press, 2009.
Rubin, Uri. The Eye of the Beholder: The Life of Muḥammad as Viewed by the Early Muslims. SLAEI 5. Princeton: Darwin, 1995.
Schoeler, Gregor. The Oral and Written in Early Islam. Trans. Uwe Vagelpohl and ed. James E. Montgomery. Routledge: London, 2006.
———. The Biography of Muḥammad: Nature and Authenticity. Trans. Uwe Vagelpohl and ed. James E. Montgomery. Routledge: London, 2011.
Shoemaker, Stephen J. The Death of a Prophet: The End of Muḥammad’s Life and the Beginnings of Islam. Philadelphia, PA: University of Pennsylvania Press, 2011.
Several scholarly translations of prophetic biographies can be found, but most readers (and indeed many scholars) find the idea of reading them quite daunting inasmuch as they offer translations of massive, multivolumed Arabic compositions. Nevertheless, comparing the accounts and the approaches of the various author-compilers can be illuminating. Below I list the best translations of the biographies of Ibn Isḥāq (d. 150/767), al-Wāqidī (207/822), and Ibn Kathīr (774/1373).
Alfred Guillaume, trans. The Life of Muḥammad: A Translation of Ibn Isḥāq’s Sīrat Rasūl Allāh. Karachi: Oxford University Press, 1978. (Guillaumes’s translation attempts to reconstruct Ibn Isḥāq’s work by inserting the portions missing from Ibn Hishām’s recension from that preserved by the historian al-Ṭabarī (d. 310/923). The recension of al-Ṭabarī was subsequently retranslated when his massive universal history was translated into English as The History of al-Ṭabarī, general editor Ehsan Yarshater (Albany, NY: SUNY Press, 1985–2007). For the relevant volumes, see vol. 6, Muḥammad at Mecca, trans. W. Montgomery Watt and M. V. MacDonald (1987); vol. 7, The Foundation of the Community, trans. M. V. McDonald and W. Montgomery Watt (1987); vol. 8, The Victory of Islam, trans. Michael Fishbein (1997); and vol. 9, The Last Years of the Prophet, trans. Ismail K. Poonawala, (1990).
Rizwi Faizer, Amal Ismail, and Abdulkader Tayob, trans. The Life of Muḥammad: al-Wāqidī’s Kitāb al-Maghāzī. New York: Routledge, 2011.
ʿImād al-Dīn Ibn Kathīr. The Life of the Prophet Muḥammad, 4 vols. Trans. Trevor Le Gassick. Reading, UK: Garnet, 1998–2000.
Recommended in addition to the above is Tarif Khalidi’s Images of Muhammad: Narratives of the Prophet in Islam Across the Centuries (New York: Doubleday, 2009), which collects samples of the prophetic biographies from diverse genres and traditions across the centuries.