If you’re reading fast you’re not thinking and challenging what you’re reading. You’re not being critical. You’re not making connections with existing knowledge. You’re not arguing with the author. You’re not reading something at the edge of your cognitive ability
Reading fast gives you two things that should never mix: surface knowledge and overconfidence.
The secret to reading better is reading lots of good books slowly. This enables you to build knowledge. Knowledge, in turn, allows you to read faster with true comprehension and retention. It’s how you can dispose of most ‘new’ books as re-hashed old ideas that offer little value.