No matter how many times you read, re-read and re-re-read, you're bound to find mistakes in anything you've written. It's best to find them before the book is published.
Back in 2009, just minutes before I had planned to send a book to the printer, I decided to check my table of contents. I had a feeling that as I changed the length of some chapters, a page number might have changed.
I actually found three wrong page numbers, and two chapters were missing from the table.
Apparently, I didn't learn the lesson well enough.
Another time I was trying to find a chapter in one of my books that has many chapters. I couldn't find it by flipping through the pages, and I couldn't find it by studiously scanning the table of contents.
When I looked even more carefully, I realized that the last entry at the bottom of one page of the TOC was Chapter 51, but the first entry on the top of the next page was Chapter 53.
There was no listing for Chapter 52.
I feel like a blind idiot.
(IMPORTANT WARNING: Any time you fix an error in a book, you may create more errors.)