If you are keeping a blog anyway (like the author did), then the marginal effort to edit/repackage your best work into a book is not that great.
(Another data point: I have a math blog, and did the same ebook repackaging for 12 of my favorite topics; it's an Amazon as a Kindle ebook/paperback & PDF on my site, makes low 4-figures monthly).
If you write on an evergreen topic (management philosophy, math, etc.), the effort can definitely be worth it. Of course, having an established audience helps (So start the blog today! In 12-18 months of not-too-much writing effort, the book may emerge.)
(Another data point: I have a math blog, and did the same ebook repackaging for 12 of my favorite topics; it's an Amazon as a Kindle ebook/paperback & PDF on my site, makes low 4-figures monthly).
If you write on an evergreen topic (management philosophy, math, etc.), the effort can definitely be worth it. Of course, having an established audience helps (So start the blog today! In 12-18 months of not-too-much writing effort, the book may emerge.)