Judith Butler: From Norms to Politics is a very good introduction to Butler's work up until around 2006. It has a kind of mixed approach and method to Butler's thinking. It is in many way a chronological structure where Lloyd starts with Subjects of Desire and the continues to Precarious Life, Giving an account of Oneself and Undoing Gender. Yet, having said that, the sense is that the book is tied together thematically rather than chronologically. Lloyd lets certain themes run through the book, for example desire and psychoanalysis, feminism and subversion. These themes are of course influenced by Butler's most influential book, Gender Trouble, yet I think Lloyd manages to show how they run through almost all of Butler's thinking. To my mind, the book is particularly strong on Butler and Feminism and it does not get as stuck on queer theory as some commentators tend to do.
A slightly annoying thing in the book are the constant references forward in the book to chapter 6, as if everything will be dealt with there (and then references in chapter 6 back to previous chapters!). Chapter 6 is a good summary of the previous book, yet I think the references could have been dealt with differently.
Anyway, this is certainly a good starting point if one wants to be introduced to Butler. Having said that I think Salih's book on Butler is still the book for an introduction to Butler.