Okay, habermas is hard. An 'introduction' to habermas which is accessible may be impossible. Given that, I think this book does a good job. It's only 110 pages, includes an interview w mr hab from which you can feel a bit of a human, and presents a decent amount if material. Of course, despite being an introduction it is full if jargon and it will be hard to read. But hey, that's kind of standard for any sociology book these days.