Triss is from Abnegation, but when her aptitude test is inconclusive she learns that she is Divergent, which many consider dangerous enough to kill her for.
Feeling she has never really belonged in Abnegation, she chooses Dauntless and undergoes the initiation, which is demanding and at times incredibly dangerous. As her talents shine through she gains enemies, willing to do whatever is needed to dispatch her so they can take her place at the top of the rankings. She also gains friends, and even a potential love interest in the form of Four, one of her Dauntless instructors.
As the final initiation task is completed and Triss enters Dauntless it becomes clear that all is not as it should be, as Erudite and Dauntless try to undermine the government and create a mindless army of Dauntless soldiers with whom they hope to seize power.
They use a serum to take control of the minds of the Dauntless and turn them into an army, but it doesn’t work on the Divergent, and Triss realises she must risk her life to save all the people she holds dear.
The book gains pace and becomes really good towards the conclusion. The scenes in which Triss is reunited with her family, and the lengths they are forced to to protect each other are really touching. I enjoyed the book, and it’s left very much open for a sequel, which should be really good as the factions are destroyed and war is obviously coming.