I want to sell eBooks on one of my websites. I want to know which module is best and simplest for this purpose. I am confused between Ubercart and eCommerce module
Simplicity is the major concern for me. Please Help me out. Thanks in advance.
From my research, you will want to use UberCart if you decide to use Drupal for your CMS. I haven't used it personally, however, from what I have been reading online, this is the only way to go if you are definately using Drupal.
Comparison article between the two: Link
There are multitudes of open source shopping cart systems out there, that are not hosted on Drupal.
+1 for Ubercart
Ubercart and e-commerce are both good solutions for running an eCommerce site on Drupal. I have mostly used Ubercart, and I think that the strong community supporting Ubercart makes it the obvious choice for me.
To suit your specific case, Ubercart comes bundled with the "File Download" (brief tutorial here) module, which allows you to add less conventional "products" (like an eBook download!) to your store.
Also, Ubercart has reached a final release (2.0), while e-commerce is still in a release candidate phase (rc13, as of this posting). I'm sure it is still suitable for a production site, but it may have some quirks and bugs still.
Ubercart has always been my go-to. I think it can be both simple and feature-rich if you need it to be.