When he gave his speech before the 2004 Democratic National Convention, Barack Obama seemed to have exploded out of nowhere, and his political career never looked back. Four years later, he was elected president, and polls now show a majority would welcome him back.

But maybe not historian and biographer David J. Garrow. The young Obama he shows in the mammoth Rising Star: The Making of Barack Obama (William Morrow, 1,078 pp., *** out of four stars) is a magnetic but calculating shape shifter who nursed presidential ambitions for far longer than he admitted or wanted anyone to know.

Garrow, who has written well-regarded and deeply researched books on Martin Luther King Jr. and the history of reproductive rights, has a huge challenge with Obama. Few presidents had already written memoirs on their own lives, as Obama had, before becoming president. Dreams From My Father, which Obama wrote after he became the first black editor of the Harvard Law Review, created the template for future books about the president.

Rising Star is Garrow’s attempt to crack that template, and he does so with a book as heavy as a paving brick and about as subtle as one heaved through a picture window.

Consider, for example, Obama’s comments about the impact his mother, Stanley Ann Dunham, had on his life. “He had never spoken so glowingly during Ann’s lifetime of her impact on his life, but in the years following her death at age fifty-two, his memories of her became far warmer than they had ever been when she was alive.”

Not content with questioning Obama’s love for his mother, Garrow goes into great detail about the future president’s relationship with his wife, Michelle, and whether his decision to marry her stemmed more from politics than love. Garrow puts great faith in the memories of Obama’s one-time girlfriend, Oberlin professor…