Adding to Ed's suggestion, there are a couple of magazine articles you might also find helpful, if you can locate copies. They're both a few years old by now. The first is an article titled "What Really Happened on Little Round Top," by Jeffrey Denman, in the August 2005 issue of Civil War Times. The other article is from North & South magazine, and is titled "Joshua L. Chamberlain and the Road to Immortality," by Glenn W. LaFantasie . It's in Volume 8, Number 4. I think LaFantasie's article was based on a book he was working on at the same time, but I have not read the book.
I used these two articles a few years ago as the basis for an online article I wrote about Chamberlain at Gettysburg, back when I was running the Civil War topic on Suite101.com. They're very good, and speak to the difference between the myth and the reality of what took place on Little Round Top, and how Chamberlain's version of what took place came to be the largely accepted version. But not without some controversy.
Here's a link to the main site for Civil War Times, and North & South -
I'm not sure if these issues are available for back-order, but they might be, and you could contact the magazines to find out. You might also be able to obtain copies through a local library, through inter-library loan, if they don't have copies on hand.
Best of luck in your research. It is a very interesting subject you've chosen.