The title of the book comes from the realization that the syntax of languages may be composed of true elements, like atoms which can normally combine only in particular ways so that certain kinds of langauges will not occur, or will do so for only for a short time before decomposing into a more stable type of language.
Linguists are still in the process of identifying these atoms and Baker is giving a popular account of the current state of investigation.
Mark C. Baker explains modern attempts to break down and categorize language by its syntax and by binary parameters that work thoughout each language providing rules that people following unconsciously in generating new utterances within any particular language.
He demonstrates that languages can be catagorized according to particular parameters which don't appear to have ANY relationship to the culture of the people speaking the language. For example, in building phrases within phrases most languages consistantly add new elements to phrases to create a larger phrase either always at the begnning of the smaller phrase or always at the end.
This seems to refute beliefs that differences in languages indicate fundamental differences in world views. Factually people of almost identical culture live side by side speaking languages that differ drastically syntactically.
So languages seemingly do NOT vary from each other in unlimited ways. Therefore there MUST be rules about what does and does not NORMALLY happen and presumably rules to the exceptions and to the exceptions to the exceptions.
These rules would be innate in human consciousness and would provide the foundations on which the actual syntax of a languages is based.
Languages can be classified syntactically according to type and sub-type and so forth entirely independantly of any genelogical relationships between them.
Baker's writing is lucid and transparent and he lets his subject matter and the puzzles it presents carry the excitement in the book.