Boy are you right about the Reinman inks!!

He degraded the first 5(?) issues' art pretty bad.
Chic Stone as usual came in & did fine work from 6-11.

But I feel that the actual stories picked up right around issue 8 (Unus), then a superhero crossover and the nice Ka-Zar/savage land change of pace. I thought 11 was the finest 'pure' Lee & Kirby issue. The art in 12, although weird by the standards of the era for a marvel book, is pretty cool for a one-time thing. The Kirby/Roth issues 13-17 were also very nice witht the Sentinels bringing back the mutant racism thing strongly & of course Juggy. Issue 20 was where the thing started to drift. Using blob & Unus as lackeys for the Lucifer 2-parter was a poor choice and of course things went downhill fast after that.

I think the title actually was on a uninterupted climb in quality (despite losing the Kirby art finishes) from 1-18.