On page 148, Lawrence Wright wrote Deraz (Essam Deraz, he is an Egyptian filmmaker and met bin Laden at his base named Lion's Den in 1988.) became bin Laden's first biographer. I suppose Lawrence Wright is the last biographer of bin Laden.
This book consists of many interviews and historical materials and the author explains the difficulty of materials' credibility in ACKNOWLEDGMENTS AND NOTES ON SOURCES. He also wrote there that "A full story of al-Qaeda cannot be told until they are allowed to talk." They are parties related to 9/11 including al-Qaeda prisoners in USA.
Although Japanese have little knowledge of Muslims we are carelessly tending to judge by news or comments of critics. I recommend you this book to understand history and thinking of Muslims.