I'm building a small library for my team. Which books should it have?

I work as the team lead of a QA team and I wanted to create a small library for people in my team - and others', of course - to expand their knowledge outside the technical domain (so, no language reference books, programming cookbooks, etc.).

As an example, I was thinking of adding "The Ideal Team Player" by Lencioni, which I found useful to use as a loose framework when hiring people.

What are your "must-read" books that I should put on this bookshelf?

Thanks!