Eisenhorn is good boilerplate sci-fi but it doesn't make good use of the setting. Too shiny, high technology too prevalent many errors that conflict with canon DA makes a habit of this. Abnetts novels are written and edited professionally and are easily accessible but bland. Eisenhorn is absurdly soft for an inquisitor at no point does the reader doubt he is the hero. His "fall" was far from convincing, he never does anything irredeemable and his motives are always pure. But he initially has a "light sabre" and uses it in Jedi fashion, defeats Chaos Marines and dreadnoughts in single combat.
Would have been better if he actually showed spiritual corruption and starting behaving insanely and make choices that the reader is shocked by. The Ian Watson novels are the in the top 5 for best wh40k and certainly the most accurate representation of the setting and especially the Inquisition.