"Personal Narrative of a Pilgrimage to Al-Madinah and Meccah" by Sir Richard Francis Burton.

Book Description (Amazon.com Review):

Volume 1 & 2 of a classic. Posing as a wandering dervish, Burton gained admittance to the holy Kaabah and to the tomb of the prophet at Medina and participated in all the rituals of the Hadj (pilgrimage). A treasury of material on Arab life, beliefs, manners and morals, etc.