There is no one holy book in Buddhism; instead, there are many thousands of texts organized into different canons, or collections of writings. However, some texts do not appear in any canon, and not all texts associated with a given school of Buddhism appear in its canon.
The Tripitaka (or Tipitaka in the original Pali) is the earliest Buddhist canon. While it was originally composed in oral form, it was put into writing in the third century B.C. and is today the only surviving Buddhist text originally created in an Indian language. It is the sole basis of Theravada Buddhism.
While the Tripitaka is already quite extensive (one modern edition includes 45 volumes), Mahayana Buddhism adds 2,184 additional texts to its canon, most of which are referred to as Sutras. Vajrayana Buddhism then takes the Tripitaka and many Mahayana Sutras and adds on a large number of Tantric texts and other works. The Tibetan Book of the Dead, or Bardo Todol, is associated with Tibetan Buddhism and through it Vajrayana Buddhism, but it does not appear in any canon.