The thermodynamic properties of coexisting solid and fluid phases are computed for the Lennard-Jones system. We make absolute Helmholtz free energy calculations for fluid and solid reference thermodynamic states and we compute differences in free energy relatively to these states in order to obtain thermodynamic properties in a range of temperatures and densities. For the free energy difference calculations we use a previously developed method [A. L. Ferreira and M. A. Barroso, Phys. Rev. E 61, 1195 (2000)]. Our results are compared with others available in the literature. Furthermore, we present absolute values of the Helmholtz free energy along solid-fluid coexistence lines.