Using the new time-of-flight photoelectron-photoelectron coincidence technique, we have recorded complete single and double photoelectron spectra of mercury at up to 48.4 eV photon energy. Many new satellite states of Hg+ have been located both below and above the double ionization limits, and some have been identified with the aid of relativistic electronic structure calculations. The superexcited states autoionize to Hg2+ showing considerable channel specificity, apparently related most strongly to the atomic shell configurations of the final states. Direct double photoionization plays a relatively small part in the process of double ionization to the ground state of Hg2+.