Which version or versions of the Bible are best to read?
In a lot of ways that depends entirely on one's personal use. And so there are different factors to consider, such how easy it is to read, or how precise it is in its translation. Balancing these can be difficult, that's just the nature of translation though.
I am partial toward the English Standard Version (ESV) and New Revised Standard Version (NRSV), these are the two translations that are commonly used in most mainline Protestant churches today. The NRSV is also the most common translation among modern Catholics. So there is some wide appeal for these, and they are both regarded as really good translations.
Other very common translations in use include the New American Standard Bible (NASB), the New King James Version (NKJV), the New International Version (NIV), and the King James Version (KJV).
The general consensus tends to be that if one is wanting to do serious Bible study, it is helpful to compare translations rather than stick to only one. Obviously it would be ideal to learn Hebrew and Greek so as to read the original languages of the Bible, but barring that, comparative reading of different translations can be beneficial in expanding the scope. Again, the nature of translation being what it is, looking at how different ways the same thing was translated can help. Of course, for more casual Bible reading, it's perfectly fine to just stick to one's preferred translation.
-CryptoLutheran