I am done or "I have finished" or "I am finished" or "I finish"?

Question

I was trying to say the following and got bewildered with the different choices.> I have "To Kill a Mockingbird" on my list. I will write you about it when **I am finished reading it.**> I have "To Kill a Mockingbird" on my list. I will write you about it when **I have finished reading it.**> I have "To Kill a Mockingbird" on my list. I will write you about it when **I am done reading it.**> I have "To Kill a Mockingbird" on my list. I will write you about it when **I finish reading it.**I am not sure which one to pick. I am confused with the exact meanings of these various choices. Could someone also shed some light on what meanings the different tenses convey in a context like this.

Answer 1

All the choices you mention have clarity.

Thinking grammatically, however, I consider "I finish reading it" works best because it more closely fits with the present tense of "I have To Kill a Mockingbird on my list.