Containing 14 books with almost 1,000 chapters, Maimonides drew on the Mishnah, Tosefta, Midrash and Talmud. Considered one of the greatest works on Jewish theological studies meaning the Mishneh Torah is still studied today.
The manuscript can be seen here.
Another digitized manuscript from the British Library can be read here.
Maimonides other great work is the Guide for the Perplexed, a treatise using Jewish tradition (based on the Talmud etc) and rational philosophy.
This image is a 14th century illumination of the work, while the original was written around 1186 C.E to 1190 C.E. A popular translation done in 1903 is available for download here.
Maimonides: The Life and World of One of Civilization’s Greatest Minds Joel L. Kraemer. Via Google Books.
Hebrew Scholarship and the Medieval World edited by Nicholas de Lange. Via Google Books.
Hebrew Manuscripts of the Middle Ages by Colette Sirat. Via Google Books.
Sephardic and Mizrahi Jewry: From the Golden Age of Spain to Modern Times edited by Zion Zohar. Via Google Books.