The "Painting War" series is a series of painting guides that I whole heartedly recommend. I have several volumes and they are always packed with context, information on the conflict and uniforms, and painting guides by world class painters.
"Rome and Her Enemies" is the latest volume and on preorder now.
Since it covers until 9th Century AD it should have sections pertinent to collectors of Wargames Atlantic's Decline and Fall line.
Stateside:
https://www.brigadegames.com/paintingwar-issue-12-rome-and-her-enemies
UK:
https://www.northstarfigures.com/prod.php?prod=16953
Typical contents and details from a Painting War volume:
More excerpts from some Painting War Napoleonic volumes here:
https://wargamesatlantic.com/community/xenforum/topic/76696/napoleonic-skirmish-games
I have these two volumes:
Honestly I found them underwhelming. Lots of repetition between the two volumes, typos, no individual miniatures taken from start to finish, only basic techniques. YMMV but I would only pick them up if steeply discounted.
The Author's Desert War and Eastern Front painting guides were better.
@JTam I did consider getting the Feudal Japan one from Painting War a while ago. So good to know they are good books.
@Berggeit
All the volumes I have are very well done.
Here and there the translation to English isn't perfect but nothing inhibits understanding.
Please post a review of the Japanese volume if you ever pick it up.