Este libro es interesante.
English: This book is interesting.
Demonstrative adjectives in Spanish are words used before a noun to indicate which person or thing you are talking about (for example: this, that, those). They show how close the object is to the speaker.
Use demonstrative adjectives in Spanish to point out or identify people or things and to show their distance from you. Use 'este' forms for things near you, 'ese' forms for things near the person you are talking to, and 'aquel' forms for things far from both.
Este libro es interesante.
English: This book is interesting.
Esa casa es grande.
English: That house is big.
Aquellos coches son nuevos.
English: Those cars (over there) are new.
Estas manzanas están frescas.
English: These apples are fresh.