Excerpt from Spare Parts by Joshua Davis, plus links to reviews, author biography & more

ONE

LORENZO SANTILLAN had always been different. It might have been his head. When he was a few months old, his mother dropped him on a curb in Zitácuaro, a town of about 100,000 people in the Mexican state of Michoacán. He already had an odd, pear-shaped head, but now he developed a lump on his forehead. Laura Alicia Santillan was worried. She decided that he needed better medical attention than he was getting in Mexico, so she began the long journey to the United States, eventually slinking through a tunnel under the border with Lorenzo in 1988. Lorenzo was nine months old. She was motivated by a simple desire.

"We came to the U.S. to fix his head," she says.

She found a doctor in Phoenix who agreed to examine her son. The man said that surgery could realign Lorenzo's skull, but with a significant risk of brain damage. But, as far as the doctor could tell, Lorenzo was doing fine. The surgery would be strictly cosmetic and was otherwise unnecessary. Laura took another look at the bump above her son's right eyebrow and saw it in a new light. From that moment on, she told Lorenzo that the bump meant he was smart. "Your extra brains are in there," she told her son.

Now that Laura and Lorenzo were in the United States, there were reasons to stay. The family had barely been getting by in Mexico. After slicing off half of his right index finger in a carpentry accident, Pablo Santillan, Lorenzo's father, fed the family by disappearing into the forest for days on end with an ancient musket. He would return with skunks, squirrels, and iguanas slung over his shoulder. Laura dumped them into a stew, added some tomato, chili, and onion, and called it dinner. She was only fourteen when she married Pablo (he was twenty), and neither had made it past sixth grade. There weren't a lot of opportunities in Zitácuaro, but in the United States, Pablo had a shot at making five dollars an hour as a gardener. It seemed worth relocating.

The family moved into a two-room apartment near downtown Phoenix. A block away, prostitutes offered their services from an abandoned building. Drug dealers worked the corners. It was starkly different from Zitácuaro, where Pablo could search the forest for food. Now they lived in the middle of a big city and it wasn't possible to hunt for dinner. Laura got intermittent work as a hotel maid, and Pablo worked landscaping jobs throughout the scorching Arizona summer.

Before coming to the United States, Laura had given birth to two children: Lorenzo and his older brother, Jose. When she crossed over to the United States, she was pregnant and soon gave birth to Pablo, Jr., on U.S. soil, which meant that her third child became an American citizen. Yoliet and Fernando, a daughter and a son, were also born in the United States. The three American-born siblings would go on to have significantly more opportunities to live and work in the United States than the two who had adopted the country as their new home.

For Laura, Mexico soon became "an erased memory." But Pablo never forgot the solitude of the Mexican forest. A quiet, stoic man, he wore cowboy boots and sported a handlebar mustache so thick, it hid his mouth. He had the hard-drinking, solitary nature of a cowboy but now found himself in a vast urban desert with five children. It was a heavy load to bear. At night and on weekends, he often bought a twelve-pack of Milwaukee's Best and started working his way through it. As Lorenzo tells it, when Pablo was drunk, he became emotional. Sometimes he told Lorenzo that he loved him, other times he snapped. On one occasion, when Lorenzo was in middle school, Pablo asked his son to clean up the living room. When Lorenzo refused, Pablo grabbed an electrical extension cord and went after him.

School wasn't much better. As Lorenzo got older, his jowls bulged out but the top of his head stayed comparatively narrow, giving it an egg shape. Kids mocked him for his misshapen head and, once he got to middle school, they laughed at his unibrow. "I didn't understand why people would do that," Lorenzo says. Many days, he came home crying.

Excerpted from Spare Parts by Lindsey Davis. Copyright © 2014 by Lindsey Davis. Excerpted by permission of Farrar, Straus & Giroux. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.