A friend of mine develops on an Bible application for the iPhone, BibleXpress. Since his application includes several translations with the app, he once mentioned to me the possibility of compressing them to save space. Any compression that is done must achieve a good ratio, but more importantly, decompression must be fast. I took it upon myself to find a compression algorithm that could fit the bill.
In my test case, I worked with the NASB translation of the Bible. The raw text of this translation, minus formatting and book/chapter/verse identifiers is 3.965MB. Since the iPhone already has zlib, using gzip compression is an obvious choice. When compressed with gzip, the file size becomes 1.189MB, a significant savings. Even though bzip2 is not readily available on the iPhone (at least not that I could find), I tested its compression which produced a file size of 0.8548MB. While these mechanisms provide a significantly smaller file, when one desires a certain portion of the file, one must first decompress the entire file up to that point. This is an expensive operation on a small device such as the iPhone.