> If you write a book and I take it and embed its knowledge into my product that is so pervasive that no one needs to buy your book any more (and I don't even credit you so no one knows where that knowledge came from), to you really still have what was stolen?

The trouble with this analogy is that it proves too much.

Suppose you write a book, and so does someone else, but they have better marketing than you and then people in the market for that genre buy theirs instead of yours. Let's even stipulate that the existence of their book actually lowers your sales, because people who want that kind of book already bought theirs by the time they find out about yours and then some people don't have time to read or can't afford to buy both.

Notice that we haven't yet said a word about the contents of either book. They could be completely independent and they've never even heard of you or your book -- they "didn't even buy a copy of your book to copy it". All we know is that they're the same genre and the existence of theirs is costing you sales. By that logic all competition would thereby be "stealing", and that can't be right.

Which implies that you don't have a property right to the customers.

Yes. That's not to say that something damaging wasn't done, but nothing was stolen. Stealing/theft requires deprivation of property. It's like receiving a normal nonlethal punch in the face and calling it murder. Murder requires someone dying.

> Theft [...] is the act of taking another person's property or services without that person's permission or consent with the intent to deprive the rightful owner of it. --- https://en.wikipedia.org/wiki/Stealing