When Ada Sibelius turns 13 in 1984, she has been living an orderly albeit unconventional life. Raised by a homeschooling single father, David Sibelius, she spends most of her days by his side at the Steiner Lab, which he runs at the Boston Institute of Technology, or Bit. David and the lab staff and graduate students treat her much like a colleague, and she is immersed in mathematics and computer programming as they progress in their work in artificial intelligence. Their ongoing project is a "chatbot" called ELIXIR. All members of the team work on the project of teaching it to converse by engaging in regular text-chat sessions with it.
Ada begins to notice signs that David's memory and cognition appear to be slipping. For a while, he denies that there is a problem--but before too long, it becomes apparent that he is losing his faculties to early-onset Alzheimer's. When David is admitted to a longterm care facility, his friend and colleague Diana Liston takes Ada in. During the process of establishing legal guardianship, certain irregularities about David's vital records and background come to light. Suddenly, there is a mystery about his past, and David himself is no longer capable of explaining. However, he has left behind clues and codes that Ada can use to discover the answers.
The book mostly moves between two timeframes: 1980s and 2009. Ada's quest to unlock the mysteries of David's past extend into her adulthood, though she does discover his true identity while still into her teens. The book's narrative also extends into the future, in a segment labeled as "soon."
Listening to the audiobook, I developed an affection for Ada and found the mystery intriguing. Most of the way through, I felt the book was on its way to a four-star rating from me. But the last couple of chapters shifted my impression somewhat, ending on what felt to me as sort of an anti-humanity/pro-AI note. This might not have been the author's intent, but that was the effect, and it felt a bit cold to me.