Once again Retribution; like Ascension and Revelation, is an extremely compelling read to anyone who is a fan of the Mass Effect series. Retribution focuses on the pro-human organisation Cerberus giving you more insights on their methods used when achieving objectives whilst also continuing the cliff hanger ending of Mass Effect Ascension. As well as introducing a new character; one of the illusive man's best agent, to the mass effect universe which is highly likely that he'll be in the next game.
The only disappointment is that the storyline of Retribution derails from one of the major choice that the majority of players would have chosen in the first Mass Effect game. Nevertheless it shouldn't stop any mass effect fan from enjoying the final novel.
The most impressive thing about these novels is that every chapter either begins in an exciting way or leads to one. It is exceedingly fun to read. Furthermore it gets you pumped for the inevitable Mass Effect 3.
Lastly, it would be wise to read Ascension before Retribution.