Gosh this is a great topic and one that is very close to me. I have heard all the reasons that are usually given for why to forgive, and they just don't ring true to me.
I had 23 years of my life hijacked and that is time that is forever gone. As far as i can see, there was no purpose served by my suffering the abuse that i did all those years.
I did find a book that makes the most sense of anything i have heard so far, and the title is "Forgiving the Unforgivable"--by Beverly Flannigan The book takes a very different approach than any others i have read (and i've read alot about forgiveness)

Boo Radley