How this could be done...

proposal.py

from flask import Flask
from flask.ext.mongoengine import MongoEngine
from flask.ext.mongorest import MongoRest
from flask.ext.mongorest.views import ResourceView
from flask.ext.mongorest.resources import Resource
from flask.ext.mongorest import operators as ops
from flask.ext.mongorest import methods  


app = Flask(__name__)

// Configure your database here

db = MongoEngine(app)
api = MongoRest(app)

class Author(db.Document):
    name = db.StringField(required=True)

class AuthorResource(Resource):
    document = Author
    uri_path = '/authors/'

class Book(db.Document):
    title = db.StringField(required=True)
    author = db.ReferenceField(Author, dbref=False)

class BookResource(Resource):
    document = Book
    related_resources = {'author': AuthorResource}
    uri_path = '/books/'

@api.register(name='authors', url=AuthorResource.uri_path)
class AuthorView(ResourceView):
    resource = AuthorResource
    methods = [methods.Create, methods.Update, methods.Fetch, methods.List]

@api.register(name='books', url=BookResource.uri_path)
class AuthorView(ResourceView):
    resource = BookResource
    methods = [methods.Create, methods.Update, methods.Fetch, methods.List]

if __name__=='__main__':
    app.debug = True
    app.run(debug=True)