I don't know why this volume is drawing so much heat with reviewers here, as I think it's probably one of the better volumes in the series thus far. In the wake of Guts's departure, Griffith basically loses it and to fill the unexpected void left by what he feels is abandonment by his friend, foolishly decides to speed up his plans and devote himself to the rapid attainment of the ambition he'd been so patiently and methodically working toward his entire life. In a fit of unthinking desperation, Griffith makes a terrible miscalculation. I think it's incredibly humanizing and even more profound considering how coldly rational and detached he's been portrayed up until this point. We see more of the pieces that will lead to the confrontation between Guts and Griffith teased at in the Black Swordsman arc and the transformation that subsequently takes place in the relationship between the two and the importance of Griffith to the Band of the Hawk is called into question. It raises questions of identity and the importance of others in life in establishing a relative notion of self in subtle and brilliant ways that have been missing in the series up until this point.
There is a lot of flashing around - sometimes confusingly so - in the wake of Guts's departure as Miura tries to move the story forward. He moves it forward a year to a certain fated time, but in doing so, finds he needs to provide awkward flashbacks for things to make sense and to give context to the changes in character that have occurred, particularly for Guts and Caska, with Caska being the more interesting of the two. The relationship between the two develops along expected lines (no surprises there), but it's a kind of sweet fulfillment because of the way Miura has dealt with the messy tangle of emotions between Caska, Guts and Griffith that I think was also particularly well done. Guts is still a prisoner of his past experiences and that (quite realistically) manifests itself as his relationship with Caska is realized.
Like George R.R. Martin, reading Miura requires an investment. If you decide to hang with them, they'll eventually make it worth your while with pretty awesome character development. It just takes a longer perspective to appreciate.