  We present a detailed analysis of XMM-Newton EPIC-pn data for the Seyfert-1
galaxy NGC 4593. We discuss the X-ray spectral properties of this source as
well as its variations with time. The 0.5-10 keV spectrum shows significant
complexity beyond a simple power-law form, with clear evidence existing for a
"soft excess" as well as absorption by highly ionized plasma (a warm absorber)
within the central engine of this active galactic nucleus. We show that the
soft excess is best described as originating from thermal Comptonization by
plasma that is appreciably cooler than the primary X-ray emitting plasma; we
find that the form of the soft excess cannot be reproduced adequately by
reflection from an ionized accretion disk. The only measurable deviation from
the power-law continuum in the hard spectrum comes from the presence of cold
and ionized fluorescent iron-K emission lines at 6.4 and 6.97 keV,
respectively. While constraints on the ionized iron line are weak, the cold
line is found to be narrow at CCD-resolution with a flux that does not track
the temporal changes in the underlying continuum, implying an origin in the
outer radii of the accretion disk or the putative molecular torus of Seyfert
unification schemes. The X-ray continuum itself varies on all accessible time
scales. We detect a ~230-second time-lag between soft and hard EPIC-pn bands
that, if interpreted as scattering timescales within a Comptonizing disk
corona, can be used to constrain the physical size of the primary X-ray source
to a characteristic length scale of ~2 gravitational radii. Taken together, the
small implied coronal size and the large implied iron line emitting region
indicate a departure from the current picture of a "typical" AGN geometry.
