This remains a classic and has been for many years regarding the veneration of the Prophet Muhammad in Islam. Written by a German orientalist who spent a great deal of time in both Turkey and the Indian Sub Continent the author covers a number of chapters relevant to traditional Islam. These being the Prophets birthday and its celebration, the "Muhammadan light" and the names of the Prophet.
As the authors main studies are of Asian Islam there is extensive use of Persian, Urdu and Turkish poets such as Hafiz, Iqbal and Rumi. The author well documents her sources and there is an excellent index at the back and bibliography so should you wish you can find and read her sources for yourself.
For a traditional understanding of Islam this is an excellent place to start.