If you have the Sony, and you want some of the newer titles, then the Sony store is the place to buy them.
This may seem like a very simplistic answer, but if you want to buy some of the most current best-sellers, then that would be the place to purchase.
I use Fictionwise to acquire much of the old pulpish Sci-Fi novels from the 30s, 40s, and 50s.
Don
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