I'd suggest putting your money into something else to be honest. The online book store market is already saturated and totally dominated by Amazon and bricks & mortar stores such as Barnes & Noble.
There's also the fact that fulfillment is no light task. Amazon succeeded through having a huge mail-order infrastructure in place. And they lost millions to start with getting this into action.
I designed the logo for an amazon rival that actually competed for a while but they went out of business after about 4 years (NetMegastore - dunno if any of you heard of them).
Good luck though
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