  We study the topology of the boundary manifold of a line arrangement in CP^2,
with emphasis on the fundamental group G and associated invariants. We
determine the Alexander polynomial Delta(G), and more generally, the twisted
Alexander polynomial associated to the abelianization of G and an arbitrary
complex representation. We give an explicit description of the unit ball in the
Alexander norm, and use it to analyze certain Bieri-Neumann-Strebel invariants
of G. From the Alexander polynomial, we also obtain a complete description of
the first characteristic variety of G. Comparing this with the corresponding
resonance variety of the cohomology ring of G enables us to characterize those
arrangements for which the boundary manifold is formal.
