Is the word celui another trick to avoid repetition?
Absolument! Do you understand what it means?
I guess it stands for the book in your example?
Close. It stands for this book!
The word celui refers to something that has been mentioned before or is obvious from context. It agrees in gender and number with the noun it replaces:
Ce livre/Cet arbre
→
Celui
Cette voiture
→
Celle
Ces vêtements
→
Ceux
Ces chaises
→
Celles
For grammar lovers:
Celui is called a demonstrative pronoun. It is used to replace a specific noun following a demonstrative adjective:
Ce livre ⇒ Celui
Let me see if I can use them...
Pratiquons ensemble !
Je veux acheter cette belle robe pour mon anniversaire.
Celle à droite ou celle à gauche ?
Excellent work!
To the demonstrative pronouns celui, celle, ceux and celles, you can add -ci and -là in order to indicate how near or far the object is from the speaker!