Born in Africa: The Quest for the Origins of Human Life, by Martin Meredith, tells the fascinating of how we evolved. What I find most interesting about this work is how much our categories of what a human, of the genus homo, is and what is an ape.
A lot of energy in the early years of fossil hunting was spent attempting to draw this line. We now know from genetic studies that we carry the genes of at least three other members of the genus homo. One of the definitions of a species is the ability to interbreed. If we did so with three groups of (now) extinct members of the genus homo, how much more so would it have been in the time period Meredith covers, millions of years ago in Africa?
The idea that there is a spectrum among apes and hominids frees us from the conceptual constraints about morphology, speciation, and the unanswerable philosophical question of what is human. Our past is far more complex than our ideas. With increased knowledge of our origins, we generate more and more questions.