Please, educate me about copyright laws

SIR— What are the laws regarding copyright? Recently, I was surprised to read a book on religion entitled, A grain of wheat. I was attracted by its colourful cover and thought that it was a new edition of James Ngugi’s (now Ngugi wa Thiongo) novel. The book, written by Margaret R. Decker was published in 1997 by New Wine Press. When does one’s copyright expire? Is there such a thing as expiry of copyright? Why have same titles from different authors? Eva Musana, Kampala