I have two that I can think of The Happiness Project (apologies for the gratuitous link to my blog, but I am completely evangelical about this one!). I just finished this today and it was so inspiring. It's about making small changes in your life to make it better. The book is a memoir and the author approaches the project in a really methodical, goal-oriented way, which I love. I really identified with her, and really want to start my own Happiness Project.
The second for me is What to do when I want to do everything by Barbara Sher (also published as Refuse to Choose!). It's basically about people, whom she identfies as 'scanners' who try so many different things in life and end up feeling dissatisfied because they are not following a traditional path, they haven't found their 'niche' (hint: they may not actually have one - but that's ok - neither did Da Vinci or Michaelangelo). It was a book I found in a charity shop. One man's trash is really another woman's treasure. Except I think I lent it to someone who moved away...
What are your "right books, right time"?