If you are going to Southern Sudan and want to speak Arabic with the people you meet there, memorize this book.
Arabic is famous for its dialects, which tend to be identified by the name of a country or larger region -- Egyptian Arabic, Gulf Arabic, Moroccan Arabic. That makes "Juba Arabic," the dialect of the relatively small region known as Southern Sudan, a bit of an anomaly. In fact, Juba Arabic is startlingly different from even the Arabic of Northern Sudan, which is closer to both Egyptian Arabic and Modern Standard Arabic than to Juba Arabic. If you speak MSA and/or another dialect, you will likely find Juba Arabic a bit of a shock. It drops many of the emphatic sounds you've worked to learn, compresses conjugations and pronouns, and goes faster than you're probably used to hearing Arabic. This dictionary will prepare you for all that.
The book is a fine dictionary from English to Arabic and Arabic to English, but its best feature is the extensive explanation of how the dialect works that follows the dictionary. It goes into subject and object pronouns, verb conjugations (not that there are any) and tenses, possessives, numbers, and so forth. If you just read through the dictionary part, you'll recognize lots of vocabulary (if you already speak Arabic) and be disheartened by all that's unfamiliar.
One feature that could be either good or bad, depending on your perspective: The Arabic is written using Latin letters, which is apparently common in Southern Sudan, although I saw a lot of MSA in Arabic script in Juba (always accompanied by English!). If you read Arabic script, it is disconcerting to have to take Arabic words in via Latin letters, but if you don't already read Arabic, you'll be happy to be able to pick up some Juba Arabic without having to learn the script.