Do we really have technology with the resolution to distinguish between layers of single atoms of materials?
X-rays do not allow you to look  at the material just like an microscope. You get the spacing information from the diffraction pattern of only crystalline materials and a lot of mathematics. On the other hand, atomic force microscopy may actually be able to tell you where one atomic layer starts and where it ends on a surface. For example, imagine a gold surface, onto which you deposit a layer of molecules (say on local spot by some means). AFM would allow you to create an image (again by indirect means, as it is not an optical technique) of that molecular layer.
See google images generated by AFM and you will see how fancy they are.

To the OP: A good way to studying is to rely on multiple references of the subject. Do not take everything literally. The authors are human beings after all with limited knowledge and of course they are not the experts of $every$ topic covered in the textbook. When I was a student, I used to spend a lot of time trying to decipher what the author was saying in a particular sentence. With maturity you learn that the better way (read: more scholarly way) is to look at the same topic in another book and see what the other author is saying.