Buddhism does not have a formal unity in terms of doctrine or historic revelation as Abrahamic Faiths do. As a result there is no a complete unity between Buddhists as to what the Buddhist Holy Book(s) are and some even say that there are no Buddhist Holy Books. There are the various views and opinions on the matter.
This question is a bit complicated because there are four main types of Buddhism, which are Mahayana, Theravada, Vajrayana, and Zen, and each of these has a variety of books which may be considered sacred to some extent. The oldest and most definitive such book, which is basic to Theravada Buddhism, is called the Pali Manuscript (after the ancient Pali language in which it was originally written).
Some books considered holy by Buddhists include the Triptaka which is composed of the Sutra Pitaka, Vinaya Pitaka, and the Abhidhamma Pitaka. The Lotus Sutra and the Gosho are less important and may only be holy in certain Buddhist sects like Nichiren. There are then commentaries by many great Buddhist teachers based on the teachings of the Buddha or inspired by him. Then a third category of scripture come from more esoteric sources like Bodhisattva's and Buddhas residing in different realms and the pure land.
There are views holding that there are no holy books in Buddhism, either because Buddhism does not assert Divine Revelation, so all of the books are known to be man-made, or because Buddhism does not have a strong theology and can accept the holy books of other religions.