I got this book because I love the Mass Effect series. However I was deeply disappointed. The plot was lazy, the research was non-existent, and the writing was poor quality.
The author is writing from the perspective of Anderson and Sanders, and their pursuit of information about the sentient machines known as Reapers (though it inaccurately states they are pursuing Saren, long dead at the time period this book is set). They 'lose' a male teenage biotic (biotics are people that can manipulate dark energy with implants - think scientific magic) named Nick whom they are looking after when he leaves to join a terrorist group on Omega (criminal underworld on a mined out asteroid, run by crime lord Aria T'loak). Nick is fairly one dimensional; while I am sure teenage boys are amorous, I doubt they are purely motivated by sex and girls, especially when it comes to violent revolution.
It follows the story of an autistic teenage biotic named Gillian, daughter of a Cerberus defector, and in hiding from Cerberus (prohuman supremacist group). She is being protected by a scientist / soldier who is described in previous books as a thoughtful, intelligent homosexual. In this book the teenage biotic is supposed to have 'grown out of' her autism (impossible and a grossly offensive supposition). Her protector has been transformed into a meathead with an assault rifle, and, inexplicably, heterosexual, and the kind of heterosexual who ogles strippers.
There is a major plot point in the first Mass Effect game where a major character who has biotic implants suffers crippling headaches and risks worse, but won't get them taken out because the operation is too dangerous. Yet Gillian goes and gets hers souped up and replaced in a two hour operation at a back street clinic.
The Quarians appear, which is nice as they are one of the more interesting Mass Effect races - intelligent, highly skilled engineers and space gypsies, displaced by the rebellion of the slave race they created. Throughout the three Mass Effect games the Quarian Environment Suits are a big deal; the Quarians cannot breathe most air and have to stay within special 'clean rooms', sterile bubbles or their suits at all times, or they will die. Dietz simply dispenses with this major universe factoid, describing them as wearing tied on rags.
You get more insight into Cerberus, but the insights are utterly flawed. Cerberus, an evil, secretive terrorist organisation - have a PR department. Kai Leng, one of the primary antagonists in Mass Effect 3 (and subject to one of the most satisfying kills in all three games) gets more air time. He's actually one of the more interesting characters, but again there are some ridiculous moments. He is a racist human supremacist, regarded as extreme even by his colleagues, yet in this book he is described as flirting with an Asari barmaid, eating salarian food, and working with aliens. He also breaks into his arch-enemy's flat and... eats cereal.
The story climaxes on Omega, in a working mine - another huge mistake as Omega is described as a mined out asteroid.