  The gamma-ray energy spectra of bright blazars of the LAT Bright AGN Sample
(LBAS) are investigated using Fermi-LAT data. Spectral properties (hardness,
curvature and variability) established using a data set accumulated over 6
months of operation are presented and discussed for different blazar classes
and subclasses: Flat Spectrum Radio Quasars (FSRQs), Low-synchrotron peaked
BLLacs (LSP-BLLacs), Intermediate-synchrotron peaked BLLacs (ISP-BLLacs) and
High-synchrotron peaked BLLacs (HSP-BLLacs). The distribution of photon index
(obtained from a power-law fit above 100 MeV) is found to correlate strongly
with blazar subclass. The change in spectral index from that averaged over the
six month observing period is < 0.2-0.3 when the flux varies by about an order
of magnitude, with a tendency toward harder spectra when the flux is brighter
for FSRQs and LSP-BLLacs. A strong departure from a single power-law spectrum
appears to be a common feature for FSRQs. This feature is also present for some
high-luminosity LSP-BLLacs, and a small number of ISP-BLLacs. It is absent in
all LBAS HSP-BLLacs. For 3C 454.3 and AO 0235+164, the two brightest FSRQ
source and LSP-BLLac source respectively, a broken power law gives the most
acceptable of power law, broken power law, and curved forms. The consequences
of these findings are discussed.
