The simple solution is to set yourself up as a self-employed writer, filing on Schedule C. This is e-filed as part of your Form 1040 tax returns; no documents need to be mailed anywhere.

This will allow you to properly report all of your book sales as gross income. Additionally, you will be able to deduct all of your writing-related expenses, including office supplies, travel for research related to your book, advertising, and, perhaps most importantly if you are writing from your home, the Business Use of the Home deduction. This will allow you to deduct a portion of all the costs of your home, based on the area devoted to your writing business.

I am including links to some IRS publications that you may find useful:

IRS Pub. 334 Tax Guide for Small Business

IRS Pub. 535 Business Expenses

IRS Pub. 587 Business Use of Your Home

Additionally, check with your local government if you are using anything other than your own name for your business. And, if you are selling books directly to the public, you may need to register with your state for a sales tax number.

I forgot to Add, I also created a company with an FEIN number so I don't think a simple schedule C works? Or does it? I received some letter from the IRS that I didn't file my estimated tax last fall, and they charged me from my refund so I'm all confused

What type of company did you form. You would have had to report that to the IRS when you applied for your FEIN. A sole proprietor of a single-member LLC will file on Schedule C. If you incorporated, you will have more complex tax returns, which can be prepared by TurboTax Business (Windows desktop only).