It covers the basics (sentiment analysis, tf-idf, n-gram, topic modelling, and visualization) well and the chapters on case studies are pretty helpful. The use of literature (Jane Austen's novels and more) as data also makes it more engaging to a literary minded reader.
It's just when the author says "slightly familiar with dplyr and ggplot2" on the preface, she means she is not going to explain any codes relating to these two packages. Compared to all those annotated-line-by-line codes in other online tutorials, this book may not be that accessible to a beginner.
On topic modelling, you may want to google how to determine the number of topics as more systematic approaches to such determination are not covered.