Questions & Answers about Мой спокойный друг читает книгу дома.
Russian usually drops the verb “to be” in the present tense when it just links a subject and a description.
- In English you say: My friend is calm.
- In Russian that would be: Мой друг спокойный. (literally: My friend calm.)
In your sentence, we don’t need “is” because читаeт already provides the verb:
Мой спокойный друг читает книгу дома.
literally: My calm friend reads a book at home.
So you never put a separate word for “is / am / are” in simple present statements like this. It appears in the past and future (e.g. был, будет), but not in the present.