No-ghost conditions and Laplacian instability of cosmological perturbations

I have been reading about cosmological perturbations for my degree work and I have to develop a stability analysis in the cosmological model that I study. However, in many articles about modified gravity I have read about "no-ghost conditions" or "Laplacian instabilty". Also in that articles they construct actions up to second-order of the perturbations for scalar, vector and tensor perturbations. I would like to understand about those things.

I have noticed that the literature about those topics is kind of limited or poor. I would be grateful if someone expert can help me, or recommend about textbooks, articles or lecture notes where they explain about cosmological perturbations, specifically about the topics mentioned above, becuase the most of literature studies generation of structures.