Michele Wruckers' book leaves out a huge part of the history between DR and Haiti, hence the conclusions in her book are all wrong. Her book doesn't really focuses on the Trujillo dictatorship, but rather on Dominican-Haitian relations with Dominicans getting all the blame.
Better sources, not to mention are heavily focused on the dictatorship, would be Trujillo, mi padre by Angelita Trujillo. This book is banned in the DR, but you can still get it abroad. If you buy it and decide to take it back into the country, I suggest you put over it a dust jacket of some irrelevant book. Customs officials are instructed to confiscate the book. Needless to say, the book gived a more positive look at the regime, but also goes into some pesky details that ruffles the feathers of a few families that insist they were always anti-Trujillistas when in reality that wasn't the case.
Jesús de Galíndez Era de Trujillo is a deep look into the regime with plenty of criticisms. The author was a Spaniard and lived in the country for a few years during the regime. Later he moved to NYC and taught at Columbia University. Once the manuscript that dissected the Trujillo dictatorship with precision, he was kidnapped and killed. His book is so well written, that to this day it's used in many Latin American universities are required reading to understand the workings of the quintessential Latin American dictatorship. Trujillo's regime was the most perfected of such political systems.
Those two books are really all that you need to get a hollistic and impartial idea of what was Trujillo's dictatorship from the inside out. Galindez book is readily available at Librería Cuesta and in any Dominican library.