When CUP approached us with the proposal of a second edition to our book, we first consulted graduate students and younger colleagues to test this idea on them. Their enthusiastic response convinced us of the soundness of the proposition.

In order to keep this project within realistic bounds, we did not rewrite the book, but rather TEX-ed the original text and corrected mistakes that have come to our attention. We also smoothed somewhat the presentation and homogenized the notation. Finally, in order to increase its usability, we added an index.

So, all in all, this is still essentially the same book. In particular, the text of this new edition does not reflect the developments in the field in the last 30 years. To compensate for this, we added a guide to the more recent literature at the end of the book.

In this whole project we were assisted by Peter Scholze, who read the whole manuscript, corrected many mistakes, and helped us with the proof-reading. We thank him heartily. We also thank Y. May, who assisted us in TEX-problems.

We also thank all those who pointed out mistakes in the first edition and often indicated to us how to correct them: we are thus grateful to C.-L. Chai, E. Looijenga, R. Pink, Y. Namikawa, and I. Satake. Finally, we thank the staff of CUP, and particularly D. Tranah, for their expert cooperation.