  These notes are based on a series of six lectures, given during my stay at
the CRC 701 in June/July 2008. The lecture series intended to give a survey of
some of the results for the almost Mathieu operator that have been obtained
since the early 1980's. Specifically, the metal-insulator transition is
discussed in detail, along with its relation to the ten Martini problem via
duality and reducibility.
