Inayat Khan wrote this short book for his friends who wanted an introduction to Sufism. The book includes an autobiography of the author as well as information on the Sufi thought of various things.
Articles: God; Nature; The Personal Being; Dual Aspect; Worship; Truth; The Sufis; Self-knowledge; Love; Perfection; Prophets; Sufism; Sufi Training; Manifestation; Interest And Indifference; Spirit And Matter; The Heart And Soul; Intellect.
Source and copyright Global Grey Ebooks: https://www.globalgreyebooks.com/index.html. The book can be downloaded from the Global Grey website.