Here is my list of books in different areas that are definitely worth checking out:
On the Jews in Sousa, try Marion Kaplan's "Dominican Haven: The Jewish Refugee Settlement in Sosua"
For very early days and info on the Tainos, try either "Columbus's Outpost Among the Tainos" by Kathleen Deagan, which I think is superb, or "The Tainos: Rise and Decline of the People Who Greeted Columbus" by Irving Rouse, which is also terrific.
From a Foreign Policy perspective, the best of the bunch in my humble opinion is "The Dictator Next Door: The Good Neighbor Policy and the Trujillo Regime in the dominican Republic" by Eric Roorda, though this is definitely for those International Relations geeks, and might be a bit much for the general reader!
"Why The Cocks Fight" by Michele Wucker is a great book about the history of the Haitian and Dominican peoples and their troubled history.
My favorite about the American occupation is about the murder of a man, that's told by the man's nephew years after the fact when the nephew goes to the Dominican to investigate the murder, really well done and filled with lots of interesting facts about that time in the country's history. Its called "Dead Man In Paradise" by JB Mackinnon.
Finally, "Trujillo: The Death of the Dictator" by Bernard Diederich is a terrific read - a day by day account of the plot and assassination of Trujillo told from all perspectives. A great book, but probably hard to find as I believe its out of print.
And I would be remiss if I did not mention a brand new book that I just finished last night, "The Eastern Stars" by Mark Kurlansky, about the history of San Pedro Macarois, and how baseball changed that town from the days of sugar until today. One of the best books I've ever read about the Dominican, and recommended for everyone, whether you have any interest in baseball or not, I think all who love the Dominican Republic will enjoy this suberb book!