Exploring the future of space exploration is a fascinating topic that has been the subject of many books. While my knowledge is based on information available up until September 2021, here are five notable books that examine the future of space exploration:

1. *"The Case for Mars: The Plan to Settle the Red Planet and Why We Must" by Robert Zubrin* - Zubrin outlines a compelling argument for the colonization of Mars and provides a detailed plan for achieving this ambitious goal. He explores the scientific, technical, and ethical aspects of making Mars a second home for humanity.

2. *"Packing for Mars: The Curious Science of Life in the Void" by Mary Roach* - While not exclusively focused on the future of space exploration, this book offers a humorous and informative look at the challenges and oddities of space travel. It provides insights into the physiological and psychological aspects of long-duration missions and what future astronauts might face.

3. *"The Future of Humanity: Terraforming Mars, Interstellar Travel, Immortality, and Our Destiny Beyond Earth" by Michio Kaku* - Kaku, a theoretical physicist, explores the possibilities of humanity's future beyond Earth. He discusses the potential for terraforming Mars, interstellar travel, and the advancement of technology that could enable us to become a multiplanetary species.

4. *"The High Frontier: Human Colonies in Space" by Gerard K. O'Neill* - Originally published in 1977, this classic book by physicist Gerard K. O'Neill presents a visionary concept for the colonization of space. O'Neill discusses the idea of building large, rotating space habitats in Earth's orbit to support human settlements and industries.

5. *"The Space Barons: Elon Musk, Jeff Bezos, and the Quest to Colonize the Cosmos" by Christian Davenport* - This book offers a behind-the-scenes look at the efforts of Elon Musk, Jeff Bezos, and other private space entrepreneurs in advancing space exploration. It explores their ambitions, companies (SpaceX and Blue Origin), and their impact on the future of space travel.

Please note that there may be more recent books on this topic that have been published since my last knowledge update in September 2021. It's a rapidly evolving field, so I recommend checking for newer publications to stay up-to-date on the latest developments in space exploration.