  We present optical spectroscopy of a sample of 77 luminous AGN and quasars
selected on the basis of their mid-infrared colors. Our objects are selected
from the Spitzer Extragalactic First Look Survey and SWIRE XMM-LSS fields, with
a typical 24mu flux density of 5mJy. The median redshift is 0.6, with a range
of ~0.05-4. Only 33% (25/77) of these objects are normal type-1 quasars, with
no obscuration. 44% (34/77) are type-2 objects, with high-ionization, narrow
emission lines, 14% (11/77) are dust-reddened type-1 quasars, showing broad
lines but a dust-reddened or unusually weak quasar continuum. 9% (7/77) show no
sign of an AGN in the optical spectrum, having either starburst spectra or
spectra which could be of either starburst or LINER types. These latter objects
are analogous to the X-ray detected population of AGN with weak or non-existent
optical AGN emission (the ``XBONGs''). 21 of our objects from the SWIRE field
fall within moderately-deep XMM exposures. All the unobscured quasars, and
about half the obscured quasars are detected in these exposures. This sample,
when taken together with other samples of Spitzer selected AGN and quasars, and
results from X-ray studies, confirms that obscured AGN dominate the AGN and
quasar number counts of all rapidly-accreting supermassive black hole systems,
at least for z~<4. This implies a high radiative efficiency for the black hole
accretion process.
