Our goal: Find what the internet ranks as the best Warhammer 40k books (instead of one person's opinion).
We searched for "best Warhammer 40k books", found the top 5 articles, took every book mentioned in 2+ articles, and averaged their rankings.
According to our research, "The Founding", "Legion", and "Fulgrim" are the top Warhammer 40k books. If you're looking for a good book, we recommend starting there! However if you're hardcore and love a good science fiction adventure, we recommend you order the entire horus heresy series (which is 93 books in total!).
You can start with Amazon, but they only added 50 or so books to the series. However, if you scroll to our header, click on the "series" tab, and search for "horus heresy"... You'll find exactly what you're looking for :)
We tried to make the list more objective than any other list on the internet. So instead of asking for one person's opinion, we looked at the opinions of 5 different trusted sources and averaged them. We believe that 1 recommendation = a subjective opinion, 2+ recommendations = closer to objective (we know it's not perfect... however it's better than the alternatives).
We recommend the same order this list is in, so our answer is "The Founding." It got the most votes and greatest rankings, and contains the opening arc in this great science fiction series.
The top answer is author Dan Abnett by far (with an astounding 10 books on our list!). But two notable mentions are author Graham McNeill (4 books), and author Aaron Dembski-Bowden (3 books). They're all incredibly popular authors with a ton of experience writing Warhammer 40k books.