I'm a huge Gemmell fan. Legend and Waylander I rate as 5/5 stars, and The First Chronicles of Druss The Legend I felt was 4.5/5. My love of those three books keeps me wanting to read every fantasy story Gemmell has ever written. That said, I haven't been blown away by all of his books — I rate In The Realm of The Wolf 3.5/5. And now having read Dark Moon, I unfortunately have a similar opinion of it.
The highlight of the book for me was Tarantino/Dace. I can't remember not enjoying any scene he (they?) was in. I found his dual nature intriguing, especially his inner-dialogue. And I was invested in his unlikely relationship with Brune — a character who I wish would have gotten even more page time.
Besides Tarantio and Brune, I also enjoyed Browyn and his mountain boat lesson, as well as Sirano's character arc and tragic end. But outside of those characters I was lukewarm on everyone else. Karis missed the mark for me, for whatever reason. And worse, I felt her death/sacrifice was contrived and didn't justify whatever moral awakening the Daroth had immediately after her demise.
Speaking of the Daroth, I was totally underwhelmed by them. And that was surprising considering I really enjoyed the antagonists in Legend, Waylander, and Chronicles of Druss.
Back to characters — Duvodas was somewhat compelling, but I never invested in his romance. And his wife's murder was handled without any surprise or subtlety in my opinion.
As for the moral philosophy of war, peace, and pacifism, Gemmell already covered those virtues and arguments in Waylander. And in my opinion he handled those topics more skillfully and memorably there.
My favorite parts of Dark Moon were: Tarantio versus the bandits and Brune; all the parts with Tarantio and Browyn; Duvodas and Tarantio getting the Pearl and freeing Sirano; and Sirano's final moments with the Daroth.
Final verdict on Dark Moon: 3/5 stars. Not a painful read but too flawed to recommend or want to read again. And definitely not up to the standard of Gemmell's best work.