No competitor is going to get better deals with UPS, Fedex and USPS. Partially because Amazon has located warehouses such that they help negotiate better shipping contracts and thus provide better customer service.
It has dumped everything that could be a profit into expansion for twenty years. A newcomer would be hard pressed to sell me a Kindle, a movie download, a used book and bearings for my clothes dryer all on the same order at an attractive price and with an aggressive delivery schedule.
If your idea might have legs, some VC will back it.
Good luck.
Y Combinator funds that sort of thing, and can help a lot with turning an idea into a growing business. You can still apply late for the Winter cycle, though if you don't have the complete team yet the Summer cycle might be better. http://www.ycombinator.com/apply
Can you be the best site for selling pewter figurines, plumbing supplies or bowling equipment? I think you can!
By niching down you can develop a reputation, have a custom-tailored search and navigation setup, etc. As you start getting more customers and income, you can broaden your offerings.
For instance pewter figures -> fantasy art -> fantasy books -> board games.
Amazon started with books before it started selling everything else. You could try the exact same strategy.
You are going to need investments to roll out an idea on this scale. But work up an initial version to prove the concept. The farther you can bootstrap it the more equity you'll retain.
As for the books. I read a lot of them. But, I came with the concept while I was reading "Zero to One" in a subway train. At one moment I got like a recovery of sight. BOOM! I closed the book without intending to open it again.
Therefore, your first step is to spend a few billion dollars building datacenters, hiring programmers and product people, and create a competitor to AWS that has approximately equal market share. That should take 5-10 years.
When you are done, you can start your e-commerce system that competes with Amazon's. You'll have the infrastructure that costs about the same (i.e. is similarly subsidized) and you'll have a fair fight.