These "Essential" collections are a welcome change from those fancy archival-type reprints that often contained poor reproductions and errors. These black & white paperbacks have at least as many problems, but not enough to keep them from being enjoyable light reading, which is exactly what they're supposed to be.
Take Thor. I wouldn't buy an expensive hardback collection of Early Thor stuff; the character isn't a favorite of mine, and he had a pretty weak start to boot. But for this price, why not?
And I had a lot of fun immersing myself in early/mid-'60s Marvel, one of my favorite eras. Thor's look and powers were pretty much set from the start, but the book's theme, supporting players, and villains had a way to go.
The Carbon Copy man? Communist Agents? Petty thugs? The only stellar villain who shows up in the early issues is Loki, The Norse God of mischief, and even he initially pulls silly stunts like turning all the cars in New York into candy.
But Loki was the start of the series' emphasis on Thor's Norse heritage, which would become a mix of myth and Jack Kirby's psychedelic imagination. After awhile, "Tales of Asgard" becomes the book's back-up series and Thor's strained relations with his father Odin (who resents his son's earth-bound love interest) becomes the primary emphasis of the main feature.
Even Thor's earthly villains seem to improve. Mr. Hyde and Cobra, two unremarkable villains, show up several times, but each story is noticably better than the last.
Anybody who likes the Marvel Thor or just likes old Marvels should enjoy this.