For somebody starting a sales career I would recommend
"Zero Resistance Selling" by Maxwell Maltz.
Most people have been taught that selling is sleezy and
a dishonorable profession and their self-confidence
suffers because of it.
This book tells how to win the game of self-confidence
in your mind - and believe me - sales WILL test your
self-esteem on many levels.
Being in sales requires YOU to take control of your
life and your results - take full responsibility. For
most people this is not something they are used to
and sales forces this upon them. Many give up in
frustration without assessing how they can improve.
The profession of sales is one that has virtually no income
ceiling and requires no college education. The only
people who are WINNERs in sales are those who can
read and improve themselves. This is a conundrum because
the people attracted to sales because of lack of education
are often deficient in ability to learn from reading and will
resist the one activity that is PROVEN to improve sales results.
It is READING books.