  New data for the differential cross sections, polarization observables $T$,
$F$, and $E$ in the reaction of $\eta$ photoproduction on proton from the
threshold up to a center-of-mass energy of W=1.9 GeV are presented. The data
were obtained with the Crystal-Ball/TAPS detector setup at the Glasgow tagged
photon facility of the Mainz Microtron MAMI. The polarization measurements were
made using a frozen-spin butanol target and circularly polarized photon beam.
The results are compared to existing experimental data and different PWA
predictions. The data solve a long-standing problem related the angular
dependence of older $T$ data close to threshold. The unexpected relative phase
motion between $s$- and $d$-wave amplitudes required by the old data is not
confirmed. At higher energies, all model predictions fail to reproduce the new
polarization data indicating a significant impact on our understanding of the
underlying dynamics of $\eta$ meson photoproduction. Furthermore, we present a
fit of the new data and existing data from GRAAL for $\Sigma$ asymmetry based
on an expansion in terms of associated Legendre polynomials. A Legendre
decomposition shows the sensitivity to small partial-wave contributions. The
sensitivity of the Legendre coefficients to the nucleon resonance parameters is
shown using the $\eta$MAID isobar model.
