Despite being one of the better 40K authors they have, Dan Abnett's contributions to the Horus Heresy series haven't been very good. Horus Rising to kick it all off was fine, but Legion was dumb because it not only turned the Alpha Legion primarch into twins, it made their motivations for siding with Horus retarded and it established this stupid precedent for 'we are such badass infiltrators we can do anything we want' that has continued in every single mention of the Alpha Legion since. I've voiced my complaints about Prospero Burns, and Know No Fear was just a disappointing collection of barely connected short stories set during the Battle for Calth. Unremembered Empire was an ok story, except that it radically changes the established canon of the end of the Heresy on Terra.
Originally, Sanguinius and the Blood Angels are on Terra while Horus had arranged for the Ultramarines to be too far away and delayed by the Word Bearer attack on Calth. Finding out the Ultramarines were almost to Terra is what prompted Horus to lower the shields on the Vengeful Spirit, leading to the final showdown with the Emperor, because he knew he couldn't resist the forces still on Terra + the Ultramarines. Now, how the hell does Sanguinius get to Terra in time to take part in the defense without Guilliman basically being a traitor for not leaving with him?