The book "Abel Sanchez" by Miguel de Unamuno

The confessional novel Abel Sanchez, or the History of Suffering is the tragic story of two friends, Joaquín Monegro and Abel Sanchez, which can be interpreted as another version of the biblical Abel and Cain, through which Unamuno tries to penetrate the depths of two historical vices peculiar only to Spain: envy and cynicism. Joaquín experiences an irresistible jealousy of Abel, especially when the latter marries Elena, the girl he loves. From that moment on, any attempt by Joaquín to forget or surpass his friend is doomed to failure, so he dedicates his life to destructive suffering, which ends first with the death of Abel and then with the death of Joaquín.