Anime and Manga Help Language Learning
The reviews for Japanese is Not That Hard and Fluent Japanese from Anime and Manga, both by Eric Bodnar, are going to be the same as these two books are so similar that I find myself questioning why the author felt the need to make them into two separate books. They are both very similar in structure and meaning to that same author's book simply called The Immersion Method. While The Immersion Method is about how to learn any language using the author’s unique language-learning method, these books—obviously—are specifically about learning Japanese. What that means is that these two books have examples in Japanese, reference other resources specific to learning Japanese, and discuss issues that are particular to learning Japanese, like tips for working with kanji.
The Fluent Japanese book is a bit longer than the Japanese is Not That Hard book, so if I were to choose one, I would pick the Fluent Japanese book. The Fluent book is similar in content to the author’s Fluent Korean book except, of course, for the specific language. So, for instance, both of the Fluent books have a tiny section on words that could be perceived as offensive, while the Japanese is Not That Hard book does not. The Fluent book also seems to have more links to a variety of Japanese language-learning resources that the other Japanese book does. There also seems to be more stress on learning the kanji as well as incorporating fun elements like anime and manga into your learning practice in the Fluent book. A whole chapter is dedicated to manga, as the author does see it as a good way in to learning how to read Japanese, which he admits can be frustrating for a Westerner.
If you have an interest in studying the Japanese language, either of these books would give you a solid method with some different practices that, combined, will help your fluency and ease with Japanese. Again, of the two, I recommend the Fluent Japanese from Anime and Manga book.
I received a free copy of both these books, but that did not affect my reviews.