  We solve the attractive Hubbard model for arbitrary interaction strengths
within dynamical mean-field theory. We compute the transition temperature for
superconductivity and analyze electron pairing in the normal phase. The normal
state is a Fermi liquid at weak coupling and a non-Fermi liquid state with a
spin gap at strong coupling. Away from half-filling, the quasi-particle weight
vanishes discontinuously at the transition between the two normal states.
