Get Firestore collection and sub-collection document data together

I have the following Firestore database structure in my Ionic 5 app.

• Book(collection)
  • {bookID}(document with book fields)
    • Like (sub-collection)
      • {userID} (document name as user ID with fields)

Book collection has documentes and each document has a Like sub-collection. The document names of Like collection are user IDs who liked the book.

I am trying to do a query to get the latest books and at the same time trying to get the document from Like sub-collection to check if I have liked it.

async getBook(coll) {
  snap = await this.afs.collection('Book').ref
    .orderBy('createdDate', "desc")
    .limit(10).get();

  snap.docs.map(x => {
    const data = x.data();
    coll.push({
      key: x.id,
      data: data.data(),
      like: this.getMyReaction(x.id)
    });
  }

async getMyReaction(key) {
    const res = await this.afs.doc('Book/myUserID').ref.get();
    if(res.exists) {
    return res.data();
  } else {
    return 'notFound';
  }
}

What I am doing here is calling the method getMyReaction() with each book ID and storing the promise in the like field. Later, I am reading the like value with async pipe in the HTML. This code is working perfectly but there is a little delay to get the like value as the promise is taking time to get resolved. Is there a solution to get sub-collection value at the same time I am getting the collection value?