The word interesting refers to anything that is attractive and appealing. It is quite synonymous to words like alluring, captivating, fascinating, exotic etc. Anything that entices or excites our senses and draws our passion, such that we attain or tend to develop a certain level of curiosity towards it, can be termed as interesting.
Something that is interesting is bound to be entertaining and stirring as well. However, just like any other adjective in the dictionary, its use is relative as well. This implies that what seems interesting to someone, needn't appeal to everyone. People have their own tastes and choices and it vastly varies with caste, creed, color, country, society etc. So if a book is termed as interesting and fascinating by a group of people, then the same book might as well be termed as dull and poorly authored by another. The use of all such adjectives in itself is quite interesting.