William Morris 
The Well at the World’s End [EPUB ebook] 

Using language with elements of the medieval tales which were his models, Morris tells the story of Ralph of Upmeads, the fourth and youngest son of a minor king, who sets out, contrary to his parents’ wishes, to find knightly adventure and seek the Well at the World’s End, a magic well which will confer a near-immortality and strengthened destiny on those who drink from it.
Although the novel is relatively obscure by today’s standards it has had a significant influence on many notable fantasy authors. C. S. Lewis and J. R. R. Tolkien both seem to have found inspiration in The Well at the World’s End: ancient tables of stone, a ‘King Peter’, a quick, white horse named ‘Silverfax’, and a character named ‘Gandalf’ are only a few, to say nothing of Ralph’s journey home as denouement, anticipating the Hobbits’ return and battle for the Shire.