Since I'm not a New Testament scholar, it is probably presumptuous of me to say that Richard Bauckham's Jesus and the Eyewitnesses is an "important" contribution to the field, but I'll go ahead and say it, it is important.
How so? Well, it presents in convincing detail why the four Gospels are closely based on eyewitness testimony of those who knew Jesus. That sentence alone should send you to the book itself. Read it. It is important.