Hi everyone, I was wondering if you guys could suggest me some good books in cosmology with finely explained WKB method and Perturbations especially in Structure formation area. I have "The early universe" by Klob and Turner and "Cosmology" by Weinberg , but they seem unpalatable at first look. I am familiar with those methods from quantum mechanics, but application to cosmology seems so confusing. E-books would be helpful, because we don't really get hard-cover books in my country. Thanks so much for concern. Regards, Genocide P.S. I am a graduate student by the way.