The crux of Moonwalking with Einstein: The Art and Science of Remembering Everything by Joshua Foer is about the transformative power of memory and how anyone can improve their ability to remember through specific techniques, practices, and mental exercises. Foer takes readers on a personal journey from being an average individual with a typical memory to becoming a U.S. Memory Champion, illustrating how memory can be trained, refined, and enhanced.

Key Themes:

1. Memory as a Skill:
   The central theme of the book is that memory is not a fixed ability but a skill that can be developed with deliberate practice. Foer demonstrates that memory can be trained using mnemonic devices, visualization techniques, and mental strategies to improve retention and recall.

2. Memory Techniques (Memory Palace):
   A major part of the book focuses on the method of loci (memory palace), a technique used by memory athletes where information is associated with specific, vivid mental images of locations in a familiar space. Foer explains how this method works and how it can be applied to everyday situations to significantly enhance memory.

3. The Science of Memory:
   Foer delves into the neuroscience behind memory, explaining how the brain processes and stores information, as well as the limits of human memory. He shows how understanding the brain’s capacity for memory can help optimize how we use it.

4. Training the Mind:
   Through Foer’s own journey of training for the U.S. Memory Championship, the book illustrates how consistent practice, discipline, and dedication can lead to remarkable improvements in memory. Foer highlights the mental discipline required to succeed and how memory athletes have honed their craft to an extraordinary level.

5. Cultural and Historical Context:
   The book also explores the historical importance of memory, especially in times when people relied on memory to store knowledge before the invention of writing and modern technology. Foer examines how different cultures and societies have used memory techniques and how these practices have evolved.

Core Message:

The core message of Moonwalking with Einstein is that memory is not a passive or fixed ability but an active skill that can be trained and improved. By understanding and applying specific memory techniques—such as the memory palace—individuals can unlock their brain's full potential to remember vast amounts of information. The book challenges the conventional idea that people have either a "good" or "bad" memory and instead promotes the idea that anyone can enhance their memory with practice and the right techniques.