Series
There are 3 books in the Ahriman series.
Published between 2012 and 2024. The publication order differs from the reading order — both are below.
Once chief librarian of the Thousand Sons, the sorcerer Ahriman now wanders the galaxy in exile, haunted by his catastrophic attempt to save his Legion. In the grim darkness of the 41st millennium, he pursues forbidden knowledge that might undo his greatest mistake. French delivers a character study
All 4 books total 2,072 pages.
The Books Oracle — track the series you are partway through, and see what to read next.