Linda Killian is a Washington journalist and author. Her latest book is “The Swing Vote: The Untapped Power of Independents.” She is studying the early republic and the roots of American democracy in the doctoral program of American University’s history department.

In September 1774, Benjamin Franklin sat down to write what is perhaps the most famous letter of reference in American history. He used the phrase “an ingenious, worthy young man” to describe Thomas Paine, an out-of-work former tax collector whom he had met in London and who was planning to sail for America. Paine made good use of Franklin’s introduction. Just a year after arriving in Philadelphia, Paine wrote “Common Sense,” which passionately argued for independence from England, and later he would become famous on both sides of the Atlantic for his writing and political theories. Franklin probably didn’t guess when he wrote the letter that Paine would become an essential voice in the fight for American independence. But he probably saw a bit of himself in the smart, curious, working-class striver with strong egalitarian political views and a streak of resentment over class, privilege and authority. Franklin also saw ingenuity. It was a quality that he possessed and that he highly prized in others.

Ingenuity is the central theme of Nick Bunker’s book about the first half of Franklin’s life. “Ingenuity” was Franklin’s favorite word, and in the 18th century it meant a combination of intellect, imagination, practical skills, wit and sociability — all traits Franklin possessed in abundance. In “Young Benjamin Franklin: The Birth of Ingenuity,” Bunker offers ample evidence to illustrate how Franklin developed ingenuity and how it influenced the rest of his life. Franklin’s origins, character and background, Bunker writes, serve to explain the man he would become.

It is the ambitious, flawed young printer Bunker is describing, not the world-famous scientist, successful businessman, prominent civic leader, diplomat, revolutionary and Founding Father who has been immortalized in countless other books. Most Americans are familiar with the rags-to-riches life story Franklin created in his “Autobiography,” published after his death. The truth is more complicated, argues Bunker, who attempts to fill in the gaps.

Bunker uses extensive original research from lesser-known sources to examine Franklin’s formative experiences, ancestors, immediate family, the patrons who helped him achieve success and the business competitors he battled along the way. Franklin had many friends and was a master at cultivating mentors who could help him. But he was not always the best judge of character in his youth, which led to numerous personal and financial difficulties. Franklin was brilliant, talented, complicated and intensely ambitious. But as a young man, Bunker asserts, he was also constantly afraid of failure.

The story begins with Franklin’s great-grandfather Henry, who was a blacksmith in Ecton in the English Midlands, about 70 miles northwest of London. From there Bunker moves more or less chronologically through Franklin’s first 40 years, stopping right on the cusp of his scientific discoveries and his later greatness as a national figure.

Franklin’s father, Josiah, was a Presbyterian Puritan and Whig who left England for Boston in 1683 seeking economic opportunity and freedom from religious and political persecution. Described as “pious and prudent” by Benjamin, Josiah was a candle- and soapmaker who sang psalms, played the violin and had a love of books that he passed on to his youngest son. Although Benjamin was forced by his father to leave school at age 10, he became a voracious reader and autodidact.

Franklin’s early struggles with organized religion and faith, and his flirtation with atheism, are explored, along with his not-always-successful quest to be good. We know so much about Franklin’s internal struggles because of the extensive letters and writings he left behind, including the “Autobiography.” Even though he wanted to project a positive image, his faults and mistakes are often on display there, including his temper and frequent lack of self-control. These are qualities Franklin strove mightily to regulate later in his life. “We remember Franklin as the apostle of hard work, temperance, and self-control,” Bunker writes. “This is the way he hoped to be remembered. But when a human being writes so much about prudence, virtue, and sobriety, it may be because he or she would prefer to be wild, intemperate, and rash. This seems to have been true of Franklin as a young man.”

Despite a heavy emphasis on Franklin’s family, friends and acquaintances, Bunker covers all the important events of his early life, including his apprenticeship at his brother’s newspaper; authorship of the Silence Dogood letters; running away to Philadelphia: his first trip to England and his time spent working in print shops there; the founding of the Junto, a networking and improvement society for Philadelphia craftsmen modeled on the English clubs he had observed in London; launching the Library Company of Philadelphia and the American Philosophical Society; writing “Poor Richard’s Almanack” and taking over the Pennsylvania Gazette; the birth of his illegitimate son William; his common-law marriage to Deborah; the birth and death of his toddler son Franky from smallpox; and the birth of daughter Sally.

This is Bunker’s third book. “An Empire on the Edge: How Britain Came to Fight America” was a Pulitzer Prize finalist in 2015. In “Young Benjamin Franklin,” Bunker offers newly discovered information about Franklin’s friends and family and vivid descriptions of the political and cultural atmosphere Franklin knew in London and Philadelphia. At times the research can be overwhelming, and Franklin’s story gets a bit lost in the details about what can seem like every person he knew in his first 40 years. But these little-known people do offer an interesting cast of characters, and many are the kind of eccentrics Franklin hugely enjoyed. They were people like Paine, whom many found annoying or a bit strange but whom Franklin appreciated.

Anyone interested in Franklin and early America should find this book fascinating. It offers important insight into the internal struggles Franklin wrestled with as a youth and the questions he strove to answer. Ultimately, though, it is as much about the emergence of the concept of ingenuity in the pre-revolutionary age and among Franklin’s intellectual and scientific mentors and friends as it is about Franklin’s own path to ingenuity.

Young Benjamin Franklin

The Birth of Ingenuity

By Nick Bunker

Knopf. 445 pp. $30