Last month, I had a unique opportunity - I was able to sit down with two guys who had done high end sales in the past, and have now since moved on to running their own companies.
I met them separately about two weeks apart. One used to sell high end audio equipment, the other raised money from accredited investors for some kind of fund.
Sales is one of those things that's crucial to everyone's lives, but rather hard to nail down. There's lots of literature available on it, but much of it is outdated - or was never even correct in the first place.
I asked both guys their favorite books on sales. Both of them replied, right away, with "SPIN Selling by Neil Rackham" - they each had separate other recommendations, but when the first book recommended on a topic by two people who have succeeded at a really high level in unrelated parts of the same field... well, you're probably on to something.
I got a copy, read it, and I'm blown away. I'm also kicking myself - Judd Weiss gave me a copy a few years ago and recommended it to me then, but my reading list was too long and I didn't get to it. Man, reading this earlier would have saved me a lot of trouble.