Advanced linear-gradient

    .book {
        background-image: linear-gradient(105deg,
                            rgba($color-white, .9) 0%,
                            rgba($color-white, .9) 50%,
                            transparent 50%
                            ),
                          url(../img/nat-10.jpg);
        background-size: cover;
        height         : 50rem;

        &__form {
            width  : 50%;
            padding: 6rem;
        }
    }