I admit that extremely detailed histories and biographies are mostly not my thing either, but there's definitely a class of books including self-help but also a lot of business books that are built around a few (or even just one) core idea. Even if fleshing out the idea beyond an article or a blog post adds color, it often really doesn't need the 250-300 pages that the publishing industry essentially requires.

I heard one author of a business book say his book was a page of content, and 200 pages of stories just to get people to read it.

Malcom Gladwell books are like this. He started out as a magazine writer and was excellent at it, his New Yorker articles are delightful. When he started writing books they just ended up being the ideas of a magazine article in book length.

This is why I find Outliers incredibly overrated. The core idea is fine, quite good even. But the fact that the book is 336 pages when it could probably be 20-50 at the most just kills the joy of reading it.

The profit motive incentivizes us to never say anything in five pages that we can get away with stretching to 5 500-page volumes.

> A book should be as long as the content merits. A lot of self-help books in the 200-300 page range (including index, notes, etc.) could be summed up in a decently long blog post.

People repeat that all the time, but I'm skeptical. I think a "summing up" would likely be less effective or persuasive than some version of the full, "repetitious" book. Repetition is usually key to actually absorbing and idea. Also, a particular formulation of an idea is unlikely to connect with every person, so if an author wants to connect with the maximum number of people, they would have to express the same idea in different ways. It's not like a book can customize itself to its reader, so every reader is exposed to all those versions, including the ones that don't connect especially well with them.

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I present you: The Hacker News Self-Help Guide to Weight-loss:

Eat less food. Exercise more. Any reasonably competent person should be able to figure out the rest from those key ideas.

Fair point, but I think your example falls on the other end of the extreme – lacking context. A sufficiently long blog post – or, better yet, a drip campaign from a newsletter over the course of a week or something and narrowly focused on a particular topic – would be able to provide context for why.

Of course, you're putting a bit of money into a book so you might be more willing to follow that advice.

All that said, I have read plenty of self-help books and I enjoy the anecdotes. IF they do help someone written as they are, more power to their authors and may that trend continue.