  We present a determination of the strong coupling constant from a fit of QCD
predictions for six event-shape variables, calculated at
next-to-next-to-leading order (NNLO) and matched to resummation in the
next-to-leading-logarithmic approximation (NLLA). These event shapes have been
measured in e+e- annihilations at LEP, where the data we use have been
collected by the ALEPH detector at centre-of-mass energies between 91 and 206
GeV. Compared to purely fixed order NNLO fits, we observe that the central fit
values are hardly affected, but the systematic uncertainty is larger because
the NLLA part re-introduces relatively large uncertainties from scale
variations. By combining the results for six event-shape variables and eight
centre-of-mass energies, we find alpha_s(MZ)= 0.1224
  +/- 0.0009 (stat)
  +/- 0.0009 (exp)
  +/- 0.0012 (had)
  +/- 0.0035 (theo), which improves previously published measurements at
NLO+NLLA. We also carry out a detailed investigation of hadronisation
corrections, using a large set of Monte Carlo generator predictions.
