Hello! I get this question a lot actually and I have formulated a decent answer for it.
Considering what a good training book depends heavily on your current stage in both personal and professional life. There are many books that aren't even closely related to sales or business yet if you're mindset is ready to appreciate discrete learning lessons you can take away a lot from even books like Ender's Shadow - which are great on their own merit. I am a digital marketing strategist for www.Unthink.me and do actually read a lot - I have personally curated a book of my top business and sales books - pick any of those and I can guarantee you that you will be learning a lot and have a real edge on competitors. https://unthink.me/books/