Buddhists have always considered Buddhism to be a religion. We’re still struggling with that label here in the West because we have a hard time untangling the ideas of “religion” and “God”, and Buddhism (in most of its forms, at least) has no concept equivalent to a supreme God.
Buddhism is a way of living, true, but that way of living is seen as a path to spiritual understanding, which is what qualifies Buddhism as a religion. The fact that God is not seen as part of that process of spiritual understanding doesn’t make Buddhism any less a religion.
While I don’t have any titles to recommend, I’d like to adjust your expectations of what you can get from reading about Buddhism your use of the words “explain” and “in depth” are what sends up red flags for me. The Buddha himself said that his teachings are “hard to understand”, and that’s quite the understatement. Viewed from the outside by a non-practitioner, it appears impenetrable, confusing and even contradictory, and any attempt to avoid or simplify those inherent difficulties does so at the expense of accuracy.
This doesn’t bother Buddhists, because they’ve always known that words are a hopeless way of conveying what Buddhist teachings are really getting at. Words make the Dharma sound like some horribly complicated conceptual scheme, when it is in fact utterly simple. But its extreme simplicity is what makes it inaccessible intellectually. Books have no choice but to speak to us via the conduit of the intellect, and the Dharma never quite emerges intact from that conduit. Fortunately, the intellect isn’t the only way in.
Read what you like, but keep in mind that reading about Buddhism is a little like reading about a piece of music: once you’ve experienced it for yourself, the words make sense; but until then, they’re just so many words.