Translation:This book writes about military strategy.
Do you know how common the given construction is?
Also, wouldn't "được viết" be better for that translation?
Được is entirely optional here. I suppose there would only be a subtle difference in that được often emphasises that a verb took place. Thus, you could picture "viết về" as meaning "is written about" whereas "được viết về" can also mean that as well as "was written about" (emphasising the verb).
A similar construction exists, for example, in "nói về" v "được nói về" = talks about/speaks of.
And duolingo VN can't even differentiate chien thuat (tactic) and chien luoc (strategy)...