1.5* rounded down
This gets the extra half star for the obviously planned plot and world. I feel the author had a distinct mental image of his world and the events that would send his characters through it. He had an exciting adventure in mind.
Unfortunately, the writing style and characterization are juvenile. Lots of simple sentences in here in the format of "Noun did Action." If that weren't clunky enough, it was abrupt, with poor transitions from one setting/scene/movement to the next, causing constant whiplash. There was little to no research put into this either, with characters who seemed to be in a medieval type setting using words and having events of modern era times, such as a surprise birthday party with presents and cake.
On top of that, the unrealistic characterization made this book difficult to get into. None of the characters here acted or reacted in the ways real humans would in the given situations. They were all a bit stupid too, even the two-hundred years old characters.
Lastly, I have one note that's about the narrator, not the book. Through parts of the narration there was a rushing sound like a fan or an air conditioner, and during another part there was a brief but distinct second voice in the background that may have been a baby's cry or a woman. Regardless, I've never heard background noise during an audiobook before, and while not overly distracting, it did take me out of the book for a few moments from time to time. Of course, this was the solo error of the narrator and not no one else.
All in all, The Rat Collector was a fun idea wrapped up in an unfortunate package. Still, I hope the author continues writing because the joy he finds in it comes through in his pages.