Would reading "The Street Bible" help me understand the KJV Bible? I've not read the Bible yet but I'm planning on purchasing the KJV Bible, once I've got the money. But I've came across a book called The Street Bible: would reading this first help me to understand KJV Bible? How different are these versions?
First of all, these two translations are extremely different.  Here's Genesis 1:1 in The Street Bible:


  First off, nothing. No light, no time, no substance, no matter. Second off, God starts it all off and WHAP! Stuff everywhere!


And in the KJV:


  In the beginning God created the heaven and the earth.


There's obviously a significant difference between these two in both translation philosophy and style.  The Street Bible is a paraphrase that attempts to use "the language of the modern urban reader."  On the other hand, the KJV is a fairly literal translation that uses Elizabethan English, which can be practically incomprehensible to some modern-day readers.

That said, though the language is very different, The Street Bible tells the same stories as the KJV and other Bibles.  Reading it will therefore increase your understanding of the Bible, and allow you to make connections to the stories in the KJV or other translations.  

Ultimately, however, the best approach is to compare a variety of translations and choose the one that is most comfortable for you. BibleGateway.com does not include The Street Bible, but it does allow side-by-side comparison between dozens of popular bible translations, such as more readable ones like the NLT and NIV and more literal ones like the NKJV and ESV.