  [abridged] We present an X-ray study of the low-luminosity active galactic
nucleus (AGN) in NGC4258 using data from Suzaku, XMM-Newton, and the Swift/BAT
survey. We find that signatures of X-ray reprocessing by cold gas are very weak
in the spectrum of this Seyfert-2 galaxy; a weak, narrow fluorescent-Kalpha
emission line of cold iron is robustly detected in both the Suzaku and
XMM-Newton spectra but at a level much below that of most other Seyfert-2
galaxies. We conclude that the circumnuclear environment of this AGN is very
"clean" and lacks the Compton-thick obscuring torus of unified Seyfert schemes.
  From the narrowness of the iron line, together with evidence for line flux
variability between the Suzaku and XMM-Newton observations, we constrain the
line emitting region to be between $3\times 10^3r_g$ and $4\times 10^4r_g$ from
the black hole. We show that the observed properties of the iron line can be
explained if the line originates from the surface layers of a warped accretion
disk. In particular, we present explicit calculations of the expected iron line
from a disk warped by Lens-Thirring precession from a misaligned central black
hole. Finally, the Suzaku data reveal clear evidence for large amplitude
2-10keV variability on timescales of 50ksec as well as smaller amplitude flares
on timescales as short as 5-10ksec. If associated with accretion disk
processes, such rapid variability requires an origin in the innermost regions
of the disk ($r\approx 10r_g$ or less).
