> I have thousands of non-fiction (mostly self-improvement) books in my reading list on GoodReads, but almost never bother to read any.

> The last few books I read were mostly filled with fluff, anecdotes, stories, jokes, and trivialities.

> I thought that online content was roughly equivalent to 80% of what I'd get from reading actual books for 20% of the effort.

For self improvement and pop-business books, it's more like you can get 99% of the value from 5% of the effort by reading about the book, or skimming it, rather than reading it closely.

> Are books worth it?

You need to know what this "it" is first. I don't mean that flippantly. Do many people find reading books useful or enriching or valuable? Oh, yes, certainly. Now: worth what? To you? Are films worth "it"? Are Casablanca, The Seventh Seal, the Up documentary series, Manos: The Hands of Fate, Cave of Forgotten Dreams, Mars Attacks!, and Debbie does Dallas, worth "it"? Are they all replaceable with a bunch of 5- to 15-minute Youtube videos?

> Is it more true for some fields than others?

Self-improvement, pop-business/leadership books, and generally anything written to sell consulting services (there's a lot of that in both those categories) are regarded as kinda jokes. If you're looking there for wisdom you're combing the desert for a pearl.

> Is it more true for older books?

The filter is that if a book is still considered good decades, centuries, or millennia after it was written, it very probably is good. Good books somtimes don't pass this filter (these are periodically rediscovered) for various reasons. But almost no bad or low-value books pass it.

> Isn't most of the information from books freely available online?

Not at all. Start studying any topic past the surface level and the only way you'll get any further "online" is buying or pirating ebooks. Keep digging—not even that far—and you'll find some that do not exist in digital form, not even on Library Genesis. If you want to seriously learn about a topic, pick up a good academic book on it, then follow up on all the books they (very probably) mention in their introduction as other major works on the topic, and maybe also the books that book directly credits as references. Often this is a faster and more accurate way to learn what the expert consensus of "foundational" works in a topic is than trying to find that out online, let alone trying to learn the information contained in those works purely online, without books (usually impossible).

> Am I missing out?

What is "it"?

> One issue for me is that books are a very big time investment. I read very slowly and I don't remember everything I read either.

Take notes.

> Even if I wanted to read books, I just don't know which ones I should start with, out of the 1000 "must-read" books in my reading list.

Stop. Pick, like, five that seem really important or that you just most want to read. Aim for variety, don't pick five all on the same topic. Ignore the rest until you're done. Don't even think about them. If you're not going to finish five there's no damn point in maintaining and stressing out over a list of 1,000. They'll still be there when you've finished your five.

One further note: as hinted at by the movie comparison above, reading a book is a process and that process is part of the effect of the book. The time it takes, the curation or generation of material by one author or editor or a team of same working together, the focus and intention of the creators, these matter. Reading 200 blog posts is not the same experience as reading a book, even if they mostly cover the same territory. A tree can become boards, but boards cannot become a tree.