Mindset by Carol Dweck. I felt like I knew the entire argument beforehand so had put of reading it. But I really, really liked it. If you have kids or work with people I would highly recommend it!

Pitch Anything by Oren Claff. The best book I have ever read on the psychology of selling. Especially person-to-person negotiations. Each time I recommend it I always think I need to read it again because I thoroughly enjoyed it.