  We present Keck spectroscopic measurements of the millisecond pulsar binary
J2215+5135. These data indicate a neutron-star (NS) mass M_NS=1.6Mo, much less
than previously estimated. The pulsar heats the companion face to T_D~9000K;
the large heating efficiency may be mediated by the intrabinary shock
dominating the X-ray light curve. At the best-fit inclination i=88.8deg, the
pulsar should be eclipsed. We find weak evidence for such eclipses in the
pulsed gamma-rays; an improved radio ephemeris allows use of up to 5 times more
Fermi-LAT gamma-ray photons for a definitive test of this picture. If
confirmed, the gamma-ray eclipse provides a novel probe of the dense companion
wind and the pulsar magnetosphere.
