The title is not quite right. I suspect that a marketing editor stepped in and composed the title for Black Fire: The True Story of the Original Tom Sawyer - And of the Mysterious Fires That Baptized Gold Rush-Era San Francisco. Tom Sawyer is in the book, but he is not the focus as the title suggests. He is more like string used to tie several things together loosely. Those things would include the fires of San Francisco in the 1850s and the California experiences of Samuel Clemens, not yet Mark Twain, in the 1860s.
The true central character of the story is the city of San Francisco, which was a horrible place to live in the 1850s. When it was not raining, winds were spreading fire across the city. Volunteer fire fighters could easily get stuck in the mud trying to reach a fire. Filled with fortune seekers crazy for gold, few residents of the city would waste time on building fireproof structures. Whole forests were wasted rebuilding San Francisco after six destructive fires in less than three years.
To fight the fires, men formed volunteer fire companies and acquired fire engines that required teams of men to pull them through the rough streets. What may baffle modern readers is how competitive these companies were. Usually formed from ethnic groups or East Coast gangs, they raced to be first to a fire. If several companies arrived together, they fought for the right to put out the fire. Some structures burned while men bludgeoned each other for the right to save them. Author Robert Graysmith devotes over half of the book to these companies, their formation, and the fires they fought.
The other issue addressed is whether the worst fires were natural or the work of an arsonist.
Black Fire is an interesting book and worth reading if you enjoy 19th century American history.
Graysmith, Robert. Black Fire: The True Story of the Original Tom Sawyer - And of the Mysterious Fires That Baptized Gold Rush-Era San Francisco. Crown Publishers, 2012. 268p. ISBN 9780307720566.