"On Arendt" by Patricia Johnson - Wadsworth Philosophers Series
This book initially gives a biography of Hannah Arendt and names people who influenced her thoughts. Then it discusses the main ideas within each of her works (books + articles) like The Origins of Totalitarianism, The Human Condition, Eichmann in Jerusalem: A Report on the Banality of Evil, etc. However, it is obvious that only an abstract of those ideas are extracted and the role of this book is to help the reader to decide whether he wants to read Arendt's works or not.
Arendt didn't establish an organized philosophical system, but taught some fundamental instructions besides her main ideas. For instance, her attention to "thinking" and noting that morality should not be commenced by rules and theories but by the process of thinking. This suspicion to theories and their rigidity may be what hindered her from establishing her thoughts in theories.
The most important thing about her was that she had "concerns" about the real world around her and didn't just write books and articles about intangible concepts as many philosophers like Heidegger, her former professor, did.