We consider systems of N bosons in a box with volume one, interacting through a repulsive two-body potential of the form \kappa N^{3\beta-1} V(N^\beta x). For all 0 < \beta < 1, and for sufficiently small coupling constant κ>0, we establish the validity of Bogoliubov theory, identifying the ground state energy and the low-lying excitation spectrum up to errors that vanish in the limit of large N.