The Bitterness of the Empire is the third and last book in The Bitterness Trilogy.
Read it here.
A friend of the author wrote this review:
TBOTE captures your heart in a heart-warming fun way, while entertaining the reader. Whoever reads this will be on the edge of their seats, full of suspense. They will not be able to "put the book down," or in this case stop reading or scrolling down. It has a good ending, and is open for more writing. It is very fun and entertaining to read, and I personally recommend it to any Phineas and Ferb fan. All together, TBOTE is a heart-warming story sure to touch your heart in a fun and loving way.