How do I resolve the authors names of books in microservice world?

So I'm starting a journey down the road of microservices. I've spent some hours online trying immerse myself into this topic.

One concept I'm not quite grasping yet is the idea of not using SQL joins and therefore having a small independent database for authors and the same for books.

So I understand the following SQL:

BooksTable - id, name, authorid
AuthorsTable - id, name

select book.name, author.name from book 
join author on book.authorId = author.id

In Node.js world

index.js

app.get('/api/books' bookDomain.get());

bookDomain.js

exports.get = () => {
  const books = bookService.get();

  const authors = authorService.get();

  /*
    This is where I'm lost: how do you achieve the simple SQL 
    above? I'm assuming in the domain is where this information is 
    "joined"? am I correct?
  */
};

Services

Database1
**bookService.js**
database context

Database2
**authorService.js**
database context

expected data (something like it, basically i'm saying JSON should be the return type)

[{
  book {
    "name": "Book 1",
    "author": "Author Name 1"
  }
},
{
  book {
    "name": "Book 2",
    "author": "Author Name 2"
  }
}]

from How do I resolve the authors names of books in microservice world?