"My Father's Brain," Sandeep Jauhar's memoir of his brilliant father's descent into dementia, is poignant and illuminating.

At 76, Prem Jauhar is becoming forgetful, but brushes off his son's concerns. "Everyone forgets, son," he says. "It happens with everyone." And this is Sandeep's conundrum: Forgetfulness does happen with everyone. At what point do you know that it's something more?

Sandeep and his siblings (all are physicians) come at their father's problems from different perspectives — brother Rajiv is almost brutally clear-eyed about what is happening; sister Suneeta, who lives in Minneapolis, pushes for services and help; but Sandeep is in denial. His father is a world-renowned geneticist; surely there can't be something profoundly wrong with his brain.

As their father begins to wander, Sandeep makes excuses, but his brother is nearly at his wits' end. "Do you really believe that he can still take care of himself? He can't even work the TV! When was the last time he sent you an email?" Sandeep's brother asks. "You have to get over this concept of independence."

"My Father's Brain," subtitled "Life in the Shadow of Alzheimer's," feels piercingly honest — the disagreements among siblings, the author's stubbornness, the pain of their brilliant father growing ever more vague. At what point, Jauhar wonders, will Prem still be Prem? And then what?

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My Father's Brain

By: Sandeep Jauhar.

Publisher: Farrar, Straus & Giroux, 238 pages, $28.