The Defenders is a wildly uneven comic, as you would expect from anything that's advertised as being a "non-team" team comic. But every now and then it just clicks, and the stories in this book are from one of those good periods. The first half is entirely written by the great (and often neglected) Steve Gerber and primarily focuses on a three way battle between the Defenders, a group of mad scientists who have all surgically altered their bodies, and cosmic deity-turned self-help guru Nebulon the Celestial Man. At it's best these tales are on a par with Gerber's work on Howard the Duck, at their worst they're still incredibly fun stories with Hulk fighting a man who glued his head to a gorilla.
The second half is a series of tales by David Kraft that succeed surprisingly well at replacing Gerber. Kraft makes the odd decision to add Hellcat to the cast and manages to throw in some great tribute stories to Steve Ditko's Dr. Strange and Steranko's Nick Fury, plus a lovely Jack Kirby inspired issue with some early Keith Giffen art.
All in all one of the better Essential volumes Marvel has released.