Some great books on business (with a focus toward financial freedom) are
Millionaire Fastlane by MJ Demarco
Rich Dad Poor Dad by Robert Kiyosaki
Also, a potentially helpful perspective is that online business is simply a medium (online vs offline distinction) that businesses can partake in, which usually allows for more automated processes and scalability (among other things). It seems it still generally follows the principles (and difficulty / success rate) of businesses, like there having to be a real need or want for your product/service. There is a ton to this domain, so these are just some off the top introductory thoughts, to add to this discussion, and is by no means comprehensive.