  A simple holographic model is presented and analyzed that describes chiral
symmetry breaking and the physics of the meson sector in QCD. This is a
bottom-up model that incorporates string theory ingredients like tachyon
condensation which is expected to be the main manifestation of chiral symmetry
breaking in the holographic context. As a model for glue the
Kuperstein-Sonnenschein background is used. The structure of the flavor vacuum
is analyzed in the quenched approximation. Chiral symmetry breaking is shown at
zero temperature. Above the deconfinement transition chiral symmetry is
restored. A complete holographic renormalization is performed and the chiral
condensate is calculated for different quark masses both at zero and non-zero
temperatures. The 0^{++},0^{-+},1^{++},1^{--} meson trajectories are analyzed
and their masses and decay constants are computed. The asymptotic trajectories
are linear. The model has one phenomenological parameter beyond those of QCD
that affects the 1^{++},0^{-+} sectors. Fitting this parameter we obtain very
good agreement with data. The model improves in several ways the popular
hard-wall and soft wall bottom-up models.
