While they do exist, a good mystery story in anime is hard to come by. "Black Butler" comes to mind, with its Victorian-England setting and occasional references to Jack the Ripper or Sherlock Holmes, but any of its episodic crimes don't have much about clues, focusing on simply catching the killer in a exciting action chase. That is why "Black Butler - Book of Murder" is such a refreshing change of pace. The two part 60-minutes-each OVA (essentially the length of a feature-length film) is firstly a mystery in the classic who-done-it form, and that it takes place in the appropriate setting of the world of "Black Butler" is simply icing on the cake.Going so far as having Arthur Conan Doyle himself, a struggling writer while practicing medicine, be a character and audience perspective to the story, is a clever device. Arthur is invited on a whim to one of Ciel Phantomhive's lavish night parties, held to honor a foreign duke at the request of the Queen. The party goes ary when said guest of honor is found dead in his room. He had been killed, but the room was locked from the inside, so how? As they try to figure out the mystery, Sebastian, the talented and faithful butler to the manor, is also killed. While grieving for the death of his loyal servant, Ciel and party must figure out who the killer is, for surely it must be one among them. Arthur, as the mystery author, is tasked to lead the case and tally the clues together towards the most likely suspect.The setup is slow, but engaging once the murders take place. The whole thing plays like a well-written Agatha Christie mystery: there's a varied cast of characters with varying motives, there's a handful of unique settings within the house that are important to the case, clues are subtle and act either with purpose or as a diversion, and the solution to the case comes with a surprise twist after the culprit is taken away. Unlike most weaker mysteries, the plot sets itself in a way so that the viewer can guess the mystery as it plays out, with the clues providing just enough of a hint to guess the answer. In some cases, it's clear exactly what is happening, allowing the viewer to take great delight as the characters continue to be unaware, but important parts of the answer will likely be missing from a viewer's solution until the end. It's immensely satisfiying. Of course, repeated viewings might grow dull after knowing how the mystery ends, but that is where the humor of "Black Butler"'s recurring cast shine.While the supporting staff of the Phantomhive manor are present, they aren't given much time to mess around for comedic effect. Much of the comedy comes at the expense of Sebastian himself, and is quite entertaining. Part of the joke does require prior knowledge to the setup of the series, specifically knowing that Sebastian is a immortal demon with incredible speed and grace. This fact isn't really suggested in "Book of Murder" until the end, despite its importance, and is a the major factor in requiring the viewer to have some idea of the show before watching the otherwise enjoyable standalone OVAs. Also, part of the final ending references a new character that only appears in "Book of Circus," the loosely related third season that broadcast in the same year, and this relevance might also be lost on viewers. Otherwise, it is easy to recommend "Book of Murder" to just about anyone as a great part of the "Black Butler" story.
Production-wise, the OVA definitely improves upon the 2008 show, using moving camera shots and more impressive character animation to make this feel theatrical. I laughed a bit at how "pretty" Ciel Phantomhive is made to look with his eyelashes, and Arthur often finds himself in situations with Ciel that would inspire suggestive fan-fiction (a bit more fun here in that it doesn't go to teh extremes of season one or two). Similarly, the music and voice acting is at least as solid as it ever was. In conclusion, it's easy to recommend "Book of Murder" to fans of mystery and anime, and prior fans to "Black Butler" should find plenty reason to enjoy it as part of the canon story. It's effort to tie the story to the "Book of - " series is a bit forced, but any series issues factor only as a small part into the overall package.