What is the author's tone in the book, Drift: The Unmooring of American Military Power?

The tone of this book is filled with both humor and solemnity. The author presents her information with interjections, sometimes making commits such as interjecting an oops after describing a mistake the troops on Grenada made. This is humorous, but the subject is so serious that the reader can sense the sarcasm under the interjection. Therefore the tone may seem light at first, but when the reader begins to understand that true impact of Ms. Maddow's words, it is the heaviness of this sarcasm they are left with.