Prepositions are used to express the relationship between two or more places, persons or time or express a relationship in time or space.
Some of the prepositions are about, above, across, despite, except and so forth.
Therefore, the sentence which contains preposition is I read a book about the inventor Thomas Edison.
In the above sentence, 'above' is the prepositions, which has several uses to reference position or movement, connection with, to mean nearby or near and so forth.
In the above sentence, 'about' as a preposition refers to the connection it makes with the inventor Thomas Edison by reading a book about him.
