Hold on, I think there might be a typo in the title you've asked about. I've searched high and low, and I can't find a book or novel called 'Erasthai Lycan' – it doesn't ring a bell on Goodreads, Amazon, or any of the usual databases. Maybe the spelling is off, or it's a much more obscure piece of serialized fiction than I'm familiar with.
That said, if we're talking about how lycanthropy themes are generally explored in fiction, it's a rich field. A lot of modern stories have moved beyond the classic monster-versus-man conflict. They use the transformation as a metaphor for puberty, mental illness, or the struggle with a 'savage' inner nature that society forces you to hide. The physical change is often the least interesting part; it's the psychological and social fallout that gets deep.
Without the specific text, it's hard to pin down, but any serious exploration of lycanthropy would likely grapple with identity, the loss of control, and the terror and liberation of embracing a primal self. It's less about the fur and fangs and more about what happens to the person inside.