The Mongoliad, by Neal Stephenson, Greg Bear et al (2012-2014)

Waiting to finish all five books in the Mongoliad series led to a longer-than-usual break between posts, but was a wise decision. Anytime Neal Stephenson is involved, it's best to wait and see how things tie together in the end. There are bound to be myriad unexpected plot twists and turns, and Mongoliad did not disappoint. The Mongoliad Cycle is just one part of an ambitious "transmedia" project called The Foreworld Saga. BTW - all five novels were read on the Kindle "Cloud Reader" platform.

Stephenson was just one member of an accomplished writing team assembled for this project, including Greg Bear and son Erik, Nicole Galland, Mark Teppo and others. Stephenson's past historical fiction accomplishments with Cryptonomicon and The Baroque Cycle had me eagerly anticipating the application of his talents to the medieval world of the Mongols, Kievan Rus and the Holy Roman Empire in the pivotal years 1241-1244

Digression: Stephenson's no slouch with science fiction, either. His latest, SEVENEVES, is a knockout.

Overall, the team writing approach produced a coherent and enjoyable tale, although marred by occasional jarring shifts in writing style that make switches between writers obvious. Various medieval mythical traditions were introduced along the way, serving as a "shadow" narrative that ties together all the historical events. Thus it becomes possible to enjoy The Mongoliad on two different levels. There's plenty of accurately reported history for me, and generous helpings of mythology, knightly chivalry and divine destiny for the King Arthur enthusiast.

A perhaps too-keen interest in medieval combat styles and weapons led to, in my opinion, overly detailed and hard-to-follow blow-by-blow descriptions of numerous single and group combat operations. Bernard Cornwell does that sort of writing more skillfully, though with less technical understanding.

It's impossible for a modern novelist to imagine the thinking of a person living eight hundred years ago, especially in relation to superstition and mythology. The authors take an interesting approach, creating some characters who are believers and are participants in various supernatural events. Other characters are skeptics who see none of the magical happenings witnessed and/or created by their compatriots.  

One extra fun thing: I always enjoy it when a historical character from one author's novel shows up in another's, especially more than one, and especially when the novels are not about the same events. In this case it was Raymond VII, Count of Toulouse. In Book 5 of The Mongoliad, Raymond is a Godot-like character who is expected but never arrives.

This same Raymond ("Raimond" in French) was a minor character in Bernard Cornwell's Grail Quest series, when the quest takes the fictional protagonist Thomas of Hookton to the south of France where he becomes embroiled in the Albigensian Crusade against Catharism.

Raymond's mother was a major character in Sharon Kay Penman's novel A King's Ransom - she was Joan (or Joanna), sister of king Richard I (Lionheart) of England.

See the Wikipedia article for a partial list of historical and mythical events and persons depicted in the ''Mongoliad'' series, along with a listing of the individual novels and authors.

The five criteria:

1. Did the novel inspire me to further historical research?

Yes. I had not previously read much on this pivotal period in medieval history. A remarkable number of significant events happened in a short period of time, in widely separated locations.
Score = 5

2. Did the novel include enough history to make it an interesting historical story?

Yes. The history was somewhat front-loaded - the first three novels included more than the last two - but all five had plenty of genuine historical interest.
Score = 5

3. Was the depiction of historical events accurate?

Yes, and/or who knows? Events of eight hundred years ago are, at best, shrouded in a thick fog of time. Events happened when and where the novels place them; so, as far as can be ascertained, the history seems pretty accurate. It's overlaid, of course, with fictionalized and fictional characters, and with various mythical narratives.
Score = 5

4. Was the depiction of historical characters accurate?

Again, who knows? Genghis Khan didn't have a Facebook page. All we can ask from historical fiction authors is that they don't mess with the history. Creating plausible and compelling fictionalized versions of historical characters is a bonus. The quality of the numerous characters in The Mongoliad was uneven, but pretty high overall.
Score = 4

5. Were the fictional or fictionalized plot and characters plausible?

Depends. The plot tying all the history together involved heaping helpings of several different medieval mythical traditions. Do I believe that the Holy Grail is/was real? No. That doesn't prevent it from working as a plot device and as part of the metaphysical underpinnings.
Score = 4