Selling eBooks on my new WP site

As you can see, this is my first ever post.

I am completely new, and after lurking around and seeing various solutions, I wanted to post one simple question:

What is the best/easiest way to sell digital eBooks on WP?

Ideally I want to easily add a PDF and ePub for each product, and let the customer choose what format they want, and have it emailed to them (or provide a link to download). (All without me having to do anything except keep adding new products.)

It seems there are a few solutions for this, but I want to know what this forum would specifically recommend. I am a newbie but I catch on quick, so your recommendations will be extremely helpful.

Hubie the Nubie

PS – I should mention, I have a credit card merchant account that works with authorize.net. I dont just want a “paypal-only” site.