Personally I don't think learned behaviors have to be unnatural. Writing and driving are learned behaviors which feel completely natural to a lot of people.
In fact, writing is an interesting example because many people say that they can think perfectly while writing by hand, but not while typing. But the ones I know who have been typing since they were extremely young, or have just been typing for a long time, often say they can think perfectly while typing. I have actually noticed the transition in myself-5 years ago it was very hard to think deeply while typing, today it's completely natural.
An e-book searching system doesn't need to be nearly as complex as typing. For example, you could theoretically have a little scrollbar that you drag your finger across and can easily anywhere from the beginning to the end of the book. In just a couple weeks I imagine this would be totally natural behavior.
In fact, writing is an interesting example because many people say that they can think perfectly while writing by hand, but not while typing. But the ones I know who have been typing since they were extremely young, or have just been typing for a long time, often say they can think perfectly while typing. I have actually noticed the transition in myself-5 years ago it was very hard to think deeply while typing, today it's completely natural.
An e-book searching system doesn't need to be nearly as complex as typing. For example, you could theoretically have a little scrollbar that you drag your finger across and can easily anywhere from the beginning to the end of the book. In just a couple weeks I imagine this would be totally natural behavior.