  In this PhD thesis, we investigate a wide class of three-dimensional massive
gravity models and show how most of them (if not all) can be brought in a
first-order, Chern-Simons-like, formulation. This allows for a general analysis
of the Hamiltonian for this wide class of models. From the Chern-Simons-like
perspective, the known higher-derivative theories of 3D massive gravity, like
Topologically Massive Gravity and New Massive Gravity, can be extended to a
wider class of models. These models are shown to be free of (possibly
ghost-like) scalar excitations and exhibit improved behavior with respect to
Anti-de Sitter holography; the new models have regions in their parameter space
where positive boundary central charge is compatible with positive mass and
energy for the massive spin-2 mode. We discuss the construction of several of
these improved models in detail and derive the necessary constraints needed to
remove any unphysical degree of freedom. We also comment on the AdS/LCFT
correspondence which arises when the massive spin-2 mode becomes massless and
is replaced by a logarithmic mode. Most of the results have been published
elsewhere, however, a special effort is made here to present the aspects of
Chern-Simons-like theories in a pedagogical and comprehensive way.
