Comparison of objects is something we have to do often. Lodash is a good partner for this!
So I had to compare this observable, with my current data. Here is how I compare them:
import {isEqual} from 'lodash';
const results = isEqual(this.books.sort(), this.userBooks$.value.sort());
if (!results || (this.userBooks$.value.length === 0)) {
this.userBooks$.next(this.books);
}