  We study the phenomenon of real space condensation in the steady state of a
class of mass transport models where the steady state factorises. The grand
canonical ensemble may be used to derive the criterion for the occurrence of a
condensation transition but does not shed light on the nature of the
condensate. Here, within the canonical ensemble, we analyse the condensation
transition and the structure of the condensate, determining the precise shape
and the size of the condensate in the condensed phase. We find two distinct
condensate regimes: one where the condensate is gaussian distributed and the
particle number fluctuations scale normally as $L^{1/2}$ where $L$ is the
system size, and a second regime where the particle number fluctuations become
anomalously large and the condensate peak is non-gaussian. Our results are
asymptotically exact and can also be interpreted within the framework of sums
of random variables. We further analyse two additional cases: one where the
condensation transition is somewhat different from the usual second order phase
transition and one where there is no true condensation transition but instead a
pseudocondensate appears at superextensive densities.
