apparently, the Dirichlet hyperbola method is no longer up-to-date, and instead Voronoi's identity is used in order to establish good bounds on the Dirichlet divisor problem.
The same applies to the Piltz divisor problem, and I'm looking for a reference explaining the corresponding generalisation of Voronoi's identity which is as readable as possible - I'm a newcomer to this subject.
I don't need the very sharpest bounds, I just want to understand the modern ("Voronoi") methods that use Bessel functions.
Thanks very much in advance!