"This book is very new."
Translation:Este libro es muy nuevo.
Hola lubita y Barbara: Being "new" is a permanent quality of the book so we use "es". Yes, some day it will be considered "old", but for now it is the quality of the book, a description of the book, therefore, "es". However........if you say "The book is wet" (because you spilled your Coke on it), you would say "El libro está mojado" because it is a temporary condition of the book, you can wipe it off, it will dry soon, .....BUT...it is still new.
este for masculine nouns. Este libro es muy nuevo. This book is very new.
esta for feminine nouns. Esta casa es muy nueva. This house is very new.
esto without a noun, when the gender is not known. Esto es muy nuevo. This is very new.
está is the present tense third person singular for éstar'.
The difference between ser and estar is not really a matter of being permanent vs temporary. That's just a rule of thumb.
"Ser" is used for descriptions, which are often permanent. But it's used for all descriptions, even things like newness which don't last. It's also used for occupations, and place of origin.
"Estar" is used for conditions, which are often temporary. It's also used for locations which are often permanent.