if you are really serious about learning nicaraguan history and...if you can read and understand some basic spanish...i strongly recommend a historical novel "el burdel de las pedrarias" written by ricardo pasos marciacq...i am not kidding...this book is written in a style of historical novel and
very closely resembles novels of james michener. it took me some two months to read it...but it was an effort that paid back big time...not only i learned some history but also i improved my spanish a lot.
cost of this book was 280 cords... good luck