You might be interested to know that the academic book field matches the story JK tells here. Income from the books doesn't amount to much when divided by the time spent on the work. If you're furloughed or unemployed, it's income, which is not to be sneezed at. But if you have another source of income it's not much. The advantage comes from experience, shoe-in-the-door, and name profile. JK is now a "well-known technical author". If he wants to write another book, or move into documentation or teaching, _Using SQLite_ looks terrific on his CV. If SQLite gets in the news (Big leak from a SQLite database ? Someone publishes a ton of useful information as a SQLite database ? News media picks up on "over a billion installations" ?) JK can earn money from appearing on TV and perhaps consultancy. When an academic writes a textbook they get a great buzz from being able to teach from a textbook which has exactly what they want in it. For a few years, until new discoveries or new ways of thinking about their subject change what they would have written. In contrast SQLite is changing, but not much (on purpose).