Overall though, I think books are overrated. Many of them have about as much quality info as a good <20 minute TED talk or a solid 15-page blog post. I assume that's because authors are pressured to inflate whatever they're trying to say until it reaches at least "book length" (~100 pages).

This statement needs some qualification. A book like Thinking fast and slow is a dense exploration of new concept and worth every single page in it. Thinner books suffer from your criticism though, they are barely worth more than a couple of good blog posts.

Personally I am inclined to read and buy books with more than 300 pages, as the books longer than that are surprisingly information dense and shorter ones surprisingly empty.

I wonder how much insight can be pressed in ever less words until it becomes a tweet.