EVIL Josh Powell slowly poisoned his tragic wife Susan in the months before she disappeared from her Utah home in 2009, and the heartless fiend even starved one of their young sons to the point of malnutrition, claims a new book about the shocking crime.

In the explosive book, “If I Can’t Have You,” authors Gregg Olsen and Rebecca Morris detail the nightmare Susan and her two children endured in their house of horrors before the beautiful young mother vanished without a trace sometime during the night of Dec. 6, 2009.

Although Susan’s body has never been found, cops believe she was murdered – and Josh was always a prime suspect. He claimed he left Susan at their West Valley City home while he took their sons, Charlie and Braden, then 4 and 2, on an overnight camping trip in freezing weather in the middle of the night.

Facing increasing scrutiny, in February 2012 Josh attacked his sons with an ax and blew up the Graham, Wash., home where they’d relocated after Susan’s dis­appearance. Josh and the boys, who were 7 and 5, perished in the explosion.

While the full truth of what hap­pened to Susan may have died with her suspected killer in that fiery blaze, friends have come forward to share shocking new allegations against Josh. And they’ve provided authors Olsen and Morris with a chilling portrait of life in the Powell home.

Despite being the family bread­ winner, Susan was kept on a tight budget by her unemployed hus­band, who raged if she didn’t buy the cheap­est groceries, friends reveal. And incredibly, they say he refused to feed Charlie and Braden three meals a day.

“Susan had to research what was on sale and what store,” explained friend Michele Oreno. “Then she had to come home and put it into the computer, what she spent on every item.

“(One time) Josh was really ticked off because the week before she had spent two cents more on a can of peas than he found at another store…It got so he wouldn’t give her money for food or anything.”

According to another friend, Rachel Marini, Josh insisted that the one meal then-infant Char­lie was fed at day care was enough. She said: “ ‘That’s all he needs,’ Josh told Susan. ‘You’re not wasting my food on him because he’s just go­ing to poop it out!’”

Not surprisingly, Char­lie was diagnosed with malnutrition when he was a year old.

Those close to the loving mother also reveal Susan started to feel ill and experienced frequent bouts of nausea two months before she dis­appeared – and they suspect that Josh was poisoning her with the or­ganic smoothies he often made for her.

Meanwhile, Josh’s father Steve, a convicted sex offender, was released from a Washington State prison in March after serving nearly two years for taking photos of his neighbors’ young daughters while they were using the bathroom in their own home. Those neighbors successfully sued Powell in civil court for $2 mil­lion, and in early May they got his Puyallup house at auction to help satisfy the judgment.

The home’s new owners have agreed, at the request of Susan’s parents, to have cadaver dogs search the property “in the next few weeks” for Susan’s remains, said their attor­ney, Anne Bremner.

“(Susan’s father) is like any father would be,” Bremner added. “He doesn’t want to leave any stone un­turned.”

Mom Susan