I haven't found any books that directly answer this question, but I will introduce some books to you with my own ideas.
There is a book called Three Ways to Quantum Gravity, which mainly introduces loop quantum gravity, string theory, black hole thermodynamics, and gravitational holographic theory. Although there is no direct answer, from the definition of space, it should be that the smallest unit itself changes and the number remains unchanged (space-time is defined by nodes of three groups of field lines, and the number of nodes should remain unchanged).
String theory is a general term for a set of theories. There will be fights between different string theories. Some think that the space atoms have changed, while others think that the number has changed. However, there is a compromise thought that the two are equivalent and indistinguishable. In short, it is explained by the vague statement of quantum mechanics. You can look at Li Miao's "Tales of Superstring History" first. You can also go to Li Miao's blog or email him to ask this question, but he doesn't seem to surf the Internet much recently.
All the books I recommend are popular science books. If you want to read academic works, you should have a considerable theoretical foundation, and they are basically all in English. First, I recommend several introductory academic books: Introduction to Quantum Effect of Gravitation by Mukhanov, Supersymmetry and Supergravity by Wess, D Film by Johnson, Superstring /M Theory by Lu Jianxin ... < P > However, to understand the above introductory books, you must also have a considerable theoretical physics foundation and have studied graduate courses in theoretical physics, such as quantum field theory, general relativity and so on.