* Non-linear narrative: This is a general term for any story that doesn't follow a chronological order. It can include jumps in time, flashbacks, and flash-forwards.
* Flashback: This is a specific technique where a story temporarily shifts to an earlier time period, often to provide context or backstory.
* Flashforward: This is similar to a flashback, but it jumps forward in time instead.
* Alternating timelines: This is a common technique where a book switches between two or more timelines, often using chapter breaks or different points of view.
* Parallel narratives: This is similar to alternating timelines, but it might focus on different characters or events in each timeline.
The specific term that best describes a book that flips between the past and present will depend on how it's done and what the author's intentions are.
Let me know if you have more context about the book, and I might be able to help you find a more specific term!