  We present an approach to Jacobi and contact geometry that makes many facts,
presented in the literature in an overcomplicated way, much more natural and
clear. The key concepts are Kirillov manifolds and linear Kirillov structures,
i.e., homogeneous Poisson manifolds and, respectively, homogeneous linear
Poisson manifolds. The difference with the existing literature is that the
homogeneity of the Poisson structure is related to a principal ${\rm
GL}(1,{\mathbb R})$-bundle structure on the manifold and not just to a vector
field. This allows for working with Jacobi bundle structures on nontrivial line
bundles and drastically simplifies the picture of Jacobi and contact geometry.
Our results easily reduce to various basic theorems of Jacobi and contact
geometry when the principal bundle structure is trivial, while giving new
insights into the theory.
