If plan to sell to corporations I highly recommend "How Winners Sell" (https://www.amazon.com/How-Winners-Sell-Strategies-Competiti...)
Its theoretical enough that you will understand why you have to do somethings but practical enough that you will know what to do.
For sales motivation, I love the "Little Red Book of Sales" (https://www.amazon.com/Little-Red-Book-Selling-Principles/dp...) for when you need to kick you own behind...