  We report a field-temperature phase diagram and an entropy map for the heavy
fermion compound CeAuSb$_2$. CeAuSb$_2$ orders antiferromagnetically below
$T_N=6.6$~K, and has two metamagnetic transitions, at 2.8 and 5.6~T. The
locations of the critical endpoints of the metamagnetic transitions, which may
play a strong role in the putative quantum criticality of CeAuSb$_2$ and
related compounds, are identified. The entropy map reveals an apparent entropy
balance with Fermi liquid behavior, implying that above the N\'{e}el transition
the Ce moments are incorporated into the Fermi liquid. High-field data showing
that the magnetic behavior is remarkably anisotropic are also reported.
