I am a little relieved that The Power of Six surpasses I Am Number Four to a faint degree; that is, the story line is smoother, wider and more complex. It is no longer set in a backdrop of some small town full of close-minded locals. It takes us out of America to a sleepy town in Spain, and vice versa. A new set of characters are added: some I like, hate, and feel indifferent to for lack of depth. The old ones like Sam Goode, Six, John Smith and Sarah What's-Her-Name (seriously, I keep forgetting her last name) belong to the second category. 
 Whatever fondness I had had with Sam Goode in I Am Number Four went out the door in The Power of Six. Now he's become an affection-seeking eyeroll, competing with John Smith over the love of Six. Meanwhile, John Smith is still John Smith: lovesick and sex-starved. The only improvement to his character is his adulterous feature. He claims over and over again that he loves Sarah, but every time he sees even the faintest shadow of Six, his knees go weak. Six? She's no more than a Bella Swan: unsatisfied with one guy, therefore calling dibs on two, Sam and John. I don't know about them, but a love triangle is a terrible idea in the midst of war. People are dying. The (authors) characters should rearrange their list of priorities. 
 Marina and Adelina are two new characters that hold my interest. I admire that their characterization is more well-made than the old ones. Adelina, for one, is a complex character who has turned her back from her planet and devoted her life instead to religion. Fear pushed her to do it. But at the last minute, she remembered her duty and fought with all her might. Hector is another character I have a fondness for. He reminds me of Haymitch Abernathy in The Hunger Games because he's a drunk, but the similarity only goes about as far as that. Hector does not speak harsh dialogue, but instead titter-worthy, flowery lines that won him a special friend in Marina. 
 I would rate this two stars, as I did with I Am Number Four, because the explanation why the Mogadorians are hunting down the Gardes still hasn't materialized on any of the pages. Sure, there were a few hints here and there, but I'm growing impatient and frustrated. I don't understand the evasion of the truth. Perhaps James Frey and the two other guys he recruited had planned to reveal this major detail in the next book. Again, I would rate this two stars, but the plot development gave me a few surprises. I am a little impressed. Hence: two-point-five stars.