I think you should start with The Life of Prophet Muhammad (sav). This book is the best one i've ever read so far. The Messenger of God Muhammed (sav)
You could also read Kashf Al Mahjub by Data Sahib (RA) or books by Sheikh Abdul Qadir Gilani (RA) since both are pretty well known scholars and are Sufi's
One of the best books I've come across most recently is a book written by Pakistani ex-pat living in America. He has been highly articulate in putting his point of view to the reader. It has been written in the wake of 9/11. Highly recommended - name: "Would you like to know something about Islam?" The Time is Ripe. He has brilliantly written it to appeal the western mind.