Ian C Esslemont - Return of the Crimson Guard

Esslemont collaborated with Steven Erikson in conceiving the world of the latter's Malazan series, and while Erikson has been making the running with the novel-writing, wikipedia tells me that Esslemont's contributions are regarded as equally canonical, and that's certainly the best way to approach this one, which for all intents and purposes is part of the series proper, enriching it by drawing out more about some characters who haven't yet featured prominently in Erikson's books, and also chronicling crucial developments at the centre of the Malaz empire itself, including directly surrounding Laseen. The prose isn't quite as good as Erikson's, nor the weaving of threads as mind-bogglingly complex - Return of the Crimson Guard is more heavily military than any in the 'Malazan Book of the Fallen' series to date - but it's still very satisfying.