First, to be clear, this is not about becoming a Manager.
My career path is trending toward becoming a Technical Leader. In essence, this is similar to what others call a "Senior Engineer." To be clear, this is NOT moving into a management or technical project management role.
Rather, it's more of a leadership software engineer role. I would still be an individual contributor, but would dial-back my Lines of Code per Day in order to both lead technical projects and influence other teams in my organization.
What I'm looking for is resources that focus on being an effective leader in the tech field -- especially books, I love to read. This can also include developing interpersonal skills ("soft-skills"), but also requires strong high-level tech skills, like designing service architectures.
Most "leadership" material out there is only for management, as that's what people consider "leadership" in most organizations. So I'm looking what's been useful to others in a similar role.
Here are some examples that I've read that come to mind, by topic: