Simon R. Green's new Ishmael Jones novel is actually pretty well written, although I was kind of sad that I was pretty sure on whodunit well before the reveal. Not that the red herrings weren't distracting enough, but....
Night Train to Murder takes a lot of inspiration from Agatha Christie's Murder on the Orient Express, even if the solution is different. It also takes place over roughly an hour or so, since Sir Dennis dies about 30 minutes into the express ride between Paddington Station and Bath. Sir Dennis is a rather unpopular British Politician, having not done much beyond shady dealings and influence peddling. He's recently been promoted to head of the Ministry of Defense's Psychic Division, and is headed First Class to Bath to take on the role. As such, The Organization sends Penny and Ishmael on the train to make sure he survives the trip, since the Organization would love to have the Division owe it a favor.
It doesn't work out that well, as Ishmael discovers Sir Dennis dead of a broken neck in a locked lavatory. The car behind first class is empty, and there are only four passengers in First class besides Penny and Ishmael, all of whom had hidden motives for wanting Sir Dennis dead, as well as a host of other reasons for being on the train acting suspiciously. We also have the Conductor and the lady selling snacks running around as the only ones who seem to be passing through cars.
In the end, Ishmael figures it out not long before the train enters Bath, and almost everyone gets a semi-happy ending.
As I said, half the reason I like these is that, unlike his over the top other series, this series acknowledges the hidden world, but it's at best flavor for very real, human killers and motivations.