does anybody know a good book on calabi yau manifolds (i am a beginner) ? thanks in advance
Depending on how much of a beginner you are, you could begin by reading Barth-Hulek-Peters-Van de Ven paying particular attention to the section on K3 surfaces (which are 2-(complex)-dimensional Calabi-Yaus):
For an overview, you could try:
Other good and possibly relevant books include:
Besse, Arthur L. (1987), Einstein manifolds, Ergebnisse der Mathematik und ihrer Grenzgebiete (3), 10, Berlin, New York: Springer-Verlag,
Gross, M.; Huybrechts, D.; Joyce, Dominic (2003), Calabi–Yau manifolds and related geometries, Universitext, Berlin, New York: Springer-Verlag,
Hübsch, Tristan (1994), Calabi–Yau Manifolds: a Bestiary for Physicists, Singapore, New York: World Scientific.
I would also add the following book:
The early parts of the book include an introduction to the Riemannian geometry of Calabi-Yau manifolds. It also includes a proof of the Calabi conjecture.