This is not a terrible textbook but I found the stories and layout quite boring. The difficulty level is said to be "Intermediate to Advanced" and it does live up to that title.
However I couldn't motivate myself to finish the book, the stories seem to be written with the interest of people from the 1950s in mind and after getting halfway through and I couldn't take anymore.
If you can put up with the topics and understand the grammar (which is quite clearly explained with examples) you probably will improve your Japanese.