The Jewish historian Josephus is one of the historic sources about Masada, and it is from Josephus that the report of the mass suicide of 950 rebels in AD 66. The mass suicide has never been identified archaeologically (only about 30 skeletons have been found to date), although there is plenty evidence for the siege (including excavations at the Roman siege camp) and subsequent abandonment of the site.
SourcesN.S. Gill has several useful sources on Josephus. A virtual tour of Masada has been assembled by Lisa Katz, About's guide to Judaism.
Neil Asher Silberman. 1998. Masada. In The Oxford Companion to Archaeology, Brian Fagan editor. Oxford University Press, Oxford.