Here is a reprint of T. W. Rhys Davids' translation of the Digha Nikaya, first published in three parts in 1899, 1910 and 1921 respectively.
The Digha Nikaya or "the collection of long doctrinal lectures" of the Buddha is one of the five Nikayas or collections belonging to the Suttapitaka or "the basket of (Buddha's) discourses" which is one of the three major collections of Pali Buddhist texts, the other two being Vinayapitaka and Abhidhammapitaka. It consists of 34 long suttas of which each individual one treats intensively some particular point or points of the doctrine.
The Buddha, like other Indian teachers of his time, was taught by conversation. He followed the literary habit of his time by embodying his doctrine in set phrases, sutras, on which he enlarged on different occasions in different ways. When the Buddha died these sayings (suttas) were collected together by his disciples into the great Nikayas of which the present one is the first.