The book has been written in the spirit of Weierstrass.
Power series play the dominant role.
The treatment, being algebraic, is not restricted to complex numbers, but remains valid over any complete-valued field. This makes it applicable to situations arising from number theory. When it is specialized to the complex case, connectivity and other topological properties come to the fore. In particular, via singularities of analytic sets, topological fundamental groups can be studied. In the transition from punctual to local, i.e. from properties at a point to properties near a point, the classical work of Osgood plays an important role.