Have you been to the libary?
Otherwise it would depend on where you live..
Here in Puerto Plata there is Cafemba on C. Separacion who also order books they don?t have upon request ( or try )..
Just passing the corner to Duarte from Central Park, opposite Canal 10 building there is also a small libreria with old and new books, they have alot of what at least I cannot find elsewhere.
Very much on history of DR, and about persons in history as well.