Compared to introductory (e.g., Hopcroft and Ullman 1979) or advanced (e.g., Martín-Vide, Mitrana, and Pȃun 2004) books on formal language theory, Kracht's book emphasizes those aspects of formal language theory that are relevant to the study of natural languages, whereas the former do not.
kracht's book gives a uniform introduction, which currently does not exist at this level, to an important area of mathematical linguistics.