  We present results of the X-ray analyses of the nearby cluster of galaxies
Abell 2399 ($z=0.058$) using the XMM-Newton and Suzaku satellites. This cluster
is classified as a low surface brightness (LSB) cluster. It has a bimodal
structure in X-rays, and the X-ray-emission peaks are significantly offset from
the peaks in gas temperature. By de-projecting the annular spectra, the
temperature and electron density in the central $r<0.1r_{200}$ region are
measured to be 3.6~keV and $1.4\times10^{-3}~{\rm cm^{-3}}$, respectively. This
yields a very high gas entropy, $\sim 300~{\rm keV\,cm^{2}}$, in the central
region, comparable to the values observed in other LSB clusters. The scaled
entropy of Abell 2399 is the highest among the REXCESS cluster sample. The
spatial distribution of the member galaxies exhibits multiple substructures,
the locations of which are significantly different from those in the X-ray
image. We discovered a clear discontinuity in the X-ray brightness and
temperature distributions in the western gas clump, which provides evidence of
the presence of a cold front. Therefore, our results strongly suggest that
A2399 has experienced a merger and that the high central entropy originates
from the merger activity.
