I have just completed reading Holocaust Denial as an International Movement by Stephen Atkins (published in 2009). This book is a broad overview of the history, goals, and members of the Holocaust denial movement. It travels from Europe to North America to the Middle East to Australia examining the leaders of the Holocaust denial movement and their publications.
I found this book to be an excellent introduction to the Holocaust denial movement. I was fairly uninformed about the particulars of this movement and the book served to educate me on a broad basis. It outlined the most common arguments deniers make: arguing against the existence of gas chambers in particular, seeking to find inconsistencies in individual testimony (as if this would invalid the entire event), and claiming to be "merely asking questions" and "demanding free speech be protected". A particular interesting example is the statement frequently made by Holocaust deniers that there were no death camps in Germany at any point. This is actually true, all of the death camps were in Poland. To someone uninitiated to the idea of Holocaust denial as a unified movement rather than a fringe idea expressed by individual crazies, this book is a valuable wake-up call.
Unfortunately, the book begins to lose steam as it goes on. After the introduction and an overview of the Holocaust in general, each section follows this formula: "This is Holocaust Denier X. (S)he was born here, was educated here, and was influenced by this person and this person. (S)he wrote This Book or Newspaper expressing Holocaust denial views, and this is what happened to him/her." This formula is interesting for a while, especially for the more famous Holocaust deniers such as David Irving, David Duke, and Mahmoud Abbas, but after a certain point it feels like we have heard it all before.
If you don't know anything about the Holocaust denial movement, I would highly recommend this book as a quick and detailed way to become informed. But if you already know a lot about the movement and its argument, it's probably worth skipping in that you will most likely not learn anything. Especially after discovering a few posts on the Huffington Post about Holocaust denial, the awareness that these people are out there spreading their beliefs is extremely important and we should all be well educated about this important problem.