Before a state can force you to collect taxes on its behalf or pay its taxes you must have some sort of connection or link with that state. This link is called nexus and when we are talking about sales tax the link must be physical. However physical does not just mean offices and warehouses. It also includes the activities of employees and even third parties acting on your behalf. Once you have nexus the next step is to figure out if what you are selling is taxable.

Since you live in CA you would have nexus there. However ebooks are generally classified as a digital good and CA does not tax digital goods so there would be no requirement to collect sales tax in CA. If you decided to sell a paper version in addition it would be taxable.

If you have activities in other states or have third parties acting on your behalf in other states you may have a responsibility to collect there as different states treat sales of digital goods differently. You may contact me or re-post for information on additional states.