Takeaway: The common thread of Protestantism is diversity, focus on scripture and change.
I first heard of Protestantism: A Very Short Introduction on a podcast from Books and Culture magazine. I am a regular reader and listener to their short weekly podcast and have first heard of a number of books that I have enjoyed from them.
I am also not familiar with the Oxford Short Introduction series. But after having read this one, I will read more. There are more than 200 books in this series over a very wide range of topics. I cannot speak to the series as a whole, but I like the idea of a series that is oriented toward short books on a wide range of topics written by top scholars in the field and oriented toward an educated reader.