Thirty years ago this month Etan Patz, a 6 ½-year-old New York City schoolboy, was given something he desperately wanted: permission to walk to the school bus stop all by himself. On the Friday of Memorial Day weekend he enjoyed that new freedom for the first and only time.

He never came home. He has since been declared legally dead. And the prime suspect in the case, Jose A. Ramos, a convicted child molester who has been long imprisoned on charges in another case but will be eligible for parole in a couple of years, once had the gall to post a Web page that offered insight into the missing boy’s fate.

“As to what actually happened to Etan Patz,” Mr. Ramos wrote — on a page that caught the enraged eye of Stan Patz, Etan’s father — “if any freedom-loving American wants the true story, I kindly ask that you send $2 to my snail-mail address.” But Stan Patz didn’t want to buy Etan’s story. He wanted and still wants Mr. Ramos to tell it under oath.

Lisa R. Cohen’s “After Etan” is a complex, many-tentacled account of just how tantalizingly close Mr. Ramos has come to incriminating himself in the Patz case and just how tirelessly he has tormented prosecutors, who have said they do not have enough evidence to charge him. In a book loaded with evidence of Mr. Ramos’s pedophilia, his attraction to Etan, knowledge of the Patz family and capacity to dispose of a child-size body, Ms. Cohen makes a persuasive case that Mr. Ramos was involved. But her emphasis is less on his actions than it is on the winding, obstacle-strewn path to justice. She tells a story that is stranger than crime fiction and messier too.