I am a big Firefly fan but this book is just poorly written. It's like it was penned by an eighth grader.
The author constantly uses 'which' add-ons at the end of sentences. 'Mal went down the alley, which was the same one they had ducked down before' instead of 'Mal went down the same alley they had used before.' The author does this again and again.
The use of the same word in a sentence like, 'Jayne pulled out his gun and realized he had only one bullet left in his gun.' instead of replacing one 'gun' with 'weapon.'
The above examples may not be exact lines in the book but they are indicative of the writing style.
Also the dialogue is awful. Everyone explains their motives and thought processes out loud like they are a villain in the 1960's Batman show. Read a line, close your eyes and picture the characters saying this in the show, and you will laugh.
Again I am a huge Firefly fan but the crew of Serenity deserves a better author.