The Quest of the Holy Grail adds a spiritual dimension to the adventures of Arthur's knights. Galahad replaces Lancelot as the central figure, though he appears and disappears so often that many of the knights are engaged in a quest to find him rather than the Grail. The central concept of the Grail was never accepted by the Church, and the Quest remains a secular romance which can be interpreted as a spiritual allegory. This is done by the hermits who appear throughout the story, pointing out the meaning of each adventure. The adventures have a strong element of the magical and otherworldly, and the story is more closely structured than Lancelot, with the accomplishment of the Grail adventure by Galahad, Perceval and Bors as its centre and culmination. For a full description of the Vulgate Cycle see the blurb for the complete set.
Norris J. Lacy (born 1940) is an American scholar focusing on French medieval literature. He is the Edwin Erle Sparks Professor Emeritus of French and Medieval Studies at the Pennsylvania State University. He is a leading expert on the Arthurian legend and has written and edited numerous books, papers, and articles on the topic. In 2014 the International Arthurian Society, North American Branch, presented him an award for Lifetime Service to Arthurian Studies.
He received his Ph.D. from Indiana University and has held teaching positions at the University of Kansas, the University of California, Los Angeles, and Washington University in St. Louis. He has served as president of the International Arthurian Society. With Geoffrey Ashe he wrote The Arthurian Handbook, and he edited The Arthurian Encyclopedia and its successor, The New Arthurian Encyclopedia, a standard reference book for Arthurian works. He also oversaw the first complete English translation of the French Vulgate and Post-Vulgate Cycles, released as the five-volume Lancelot-Grail: The Old French Arthurian Vulgate and Post-Vulgate in Translation.
The Quest for the Holy Grail is, in the Vulgate Cycle, very much like some other version I've read -- Malory, I think it must be? Lots of self-flagellation on Lancelot's part, lots of glorifying Galahad, although he seems to be somewhat less insufferable in this version. Perceval's at least half-decent, too. No harping on about how ignorant and stupid he is, nor blaming it on the fact that he's Welsh. That counts as half-decent to me.
As usual, in grail stories (apart from the German one, The Crown), Gawain is faithless and sinful and horrible and blah, blah, blah. Which contrasts strongly with his characterisation earlier in the cycle. The French tradition as represented by the Vulgate and Chrétien de Troyes is particularly odd about Gawain, actually -- it often does this, where Gawain is peerless at one point and then disgraceful in another.
Like the other volumes of this series, it's well-translated, with helpful notes referring you back and forward in the text and clarifying its oddities (e.g. referring to an event it claims to have described, but which it has not even referred to before).