Daemonslayer

Gotrek & Felix join an expedition northwards in search of the long-lost dwarf hold of Karag Dum. Setting forth for the hideous Realms of Chaos in an experimental dwarf airship, the heroic pair are sworn to recover the ancient treasures or die in the attempt.

Read it because
This is the book that brings in loads of the elements of classic Gotrek and Felix – Snorri Nosebiter, Malakai Makaisson, Ulrika Magdova and Max Schrieber all make their first appearances. Plus it's a cracking tale in its own right, with a truly epic conclusion.