Martin Heidegger's Sein und Zeit is one of the seminal works in philosophy of the 20th century. It is also a very cryptic work. Martin Heidegger on Being Human relates oracular claims in plain English and supplies arguments missing in Sein und Zeit to show that its claims are plausible.
Not great, another American book trying to translate SZ into more understandable English, but just flattens over so much including basically everything about time. But who knows, I’m far from a Heidegger expert.