Look at the author's credentials for whatever book(s) you're considering. It's definitely no guarantee, but academic historical training / background is helpful. Just as a general note.
The basics: Pausanias - Descriptions of Greece Philostratus - Gymnastica Pindar - Odes John Godfrey - Science of Defense Pierce Egan - Boxiana Henry Miles - Pugilistica Frank Dowling - Fistiana Richard Fox - Lives and Battles These are all free and will give you a good base.
If you're interested in the heavyweight division : https://www.amazon.com/stores/Adam-...e&ccs_id=10a0cf0d-94a0-4a85-815e-2f02157872f9
Adam Pollack’s “In the Ring with” book series, Steve Compton’s book on Harry Greb, Clay Moyle’s book on Sam Langford. Couldn’t go wrong with any of these
Check out Boxing: The 20th century. It has such great historical details of world title fights. It's a must-have for anyone looking to delve into the history.
Gilbert odds boxing encylopedia from 1989 contains mini bios of most notable 20th century boxers and also contains a few chapters on bareknuckle boxers. This book was my intro to boxing back in 2004. Bless my wonderful mom for buying it for me. The Encyclopedia of Boxing: Odd, Gilbert E.: 9781555213954: Books - Amazon.ca
I cannot recommend the work of Springs Toledo enough. There's quite a lot of his articles up and about if you want to quality check, but his books are some or the best boxing writing I've ever read.
Newspapers You can buy a book if you're too lazy. Your outlook on the era will be given to you and your ignorance will kill any possibility of critical thought so that you become nothing more than a parrot of the author when they wrote the book. Promise they keep doing research and even change their stances when new information from someone else who reads newspapers comes out. So what you're buying is a bit of a time capsule. I don't mean to talk **** about Adam or his books. They serve a purpose and he's very good. That said, there are plenty here who think they've read a book and now know the era. They are out of date. They spread out of date information and they use the weight of authority and consensus against primary source until an author pops it into a new book. That said, if the prospect of research is too much, rely on a good researcher like Matt Dunnellon. Ain't no shame in that. Most of what they write will be true and all of what they wrote when they wrote it will be believed at that time. My only advice is stick to the mid 2000s authors and newer. Matt, Adam, Kevin, they tend to write less fantasy. Hell that's not even good enough, they do not write any fantasy in their non-fiction book. pre-2006 is a crap shoot. Bunch of authors relying on earlier authors who simply wrote stories not truth. 2006 and newer is about when the boys started to set record straight. literally. Great authors. I'm just not sure one should rely on others' research when their sources are right there for you too.