Some of the most famous books are the least worth reading. Their fame was due to their having done something that needed to be doing in their day. The work is done and the virtue of the book has expired. ↗
Every job is different. I don't think that I've ever had that wonderful feeling when you've finished a job or where you feel like you've mastered it or sort of nailed it... You can never be satisfied. If you're satisfied, it's time to retire. ↗