Out of all the Gotrek and Felix novels, this is probably among my favourites: the cloak and dagger element as the pair strive to unearth a treacherous conspiracy was so engaging, and even with the cover art spoiling the identity of the main villain ahead of time, there's still plenty of surprises, along with the usual mix of action and black humour...
"Stopping at the city of Nuln en route to the siege at Middenheim, Gotrek Gurnisson, determined to find his death in battle against the daemon hordes of Archaon, and his Rememberer Felix Jaegar reunite with their old comrade Malakai Makaisson, who offers to convey them to Middenheim, where he's due to deliver a consignment of cannons to the city's defenders. But when a series of accidents and mishaps orchestrated by a mysterious Chaos cult determined to sabotage the Imperial war effort leave the pair unable to leave, it becomes a race against time to stop the cult's apocalyptic endgame...