Too easy, SuperScrounge. The theme is that they're all comic books. Can't fool us
Ya got me!

New Sad Sack
It's a puzzle why this book is called, 'New'
I believe it was the second Sad Sack book that collected the Sad Sack cartoons. I imagine the first book has mostly strips from 1941 and 1942, while this book seems to have comics published in 1943-45.
After the Yank run I think Baker tried running civilian Sad Sack strips in the newspapers (just like a number of military strips attempted, I'm not sure how many of them had successful post-war runs though.) then he sold it to Harvey in 1949 where they restored Sad Sack to a military setting and made other changes, although I believe Baker drew covers for the comic books for years.
New Big Hit Comics
I was waiting for this book to read one of the Tripalong Hoppity episodes of this story that we were missing.
Yeah, I figured you'd like that one.

---
My Reviews
New Adventure Comics #12Captain Jim of the Texas RangersAn exciting installment.
JaneyInteresting gag.
GoofoInteresting that we hear about how good a magician he is and yet we never see his act.
The VikingsOkay. Although I was wondering why they went the caption route instead of word balloons & realized the story might have taken longer if they had the characters talk. Well, that and the writer was probably a fan of Prince Valiant.
Don CoyoteEhhh... if only the king would sentence the bratty kid to the rack. ;-)
Captain QuickOkay.
The Blood PearlsBaslyn needs to calm down. How does the Chinaman know where Baslyn went? Did he Lojack the pearls?
Rattlesnake PeteOkay.
17-20 On The BlackEh, okay.
Andy HandyCute.
EbonyEhh...
Ol' Oz BoppIs Juniper a metaphor for Humor?
SheProbably works better in the book.
LoopyWeak joke.
Castaway IslandA problem with these old 2-pagers, a dull setting up for a climax that will happen next issue.
Golden DragonHuh. One of the Major's stories adapted to a comic. I wonder if he paid himself for the adaptation rights? ;-)
Maginnis of the MountiesNice wrap-up.
Rock-Age RoyCute.
Steve ConradNow this is the way to fill in those build up moments. Include a little action as well.
Cal 'n' AlecSlow and filled with dialect 'humor'.
Sandor and the Lost CivilizationOkay.
A Tale of Two CitiesInteresting.
Chikko ChakkoWell you can hardly blame Chikko for confusing a politician with a bandit. ;-)
Sam the PorterOkay.
Hardluck HarryBit of a shaggy dog story.
Federal MenKind of funny that sci-fi story was just a story dreamed up by a present day scientist. I think it would have been better if they would have just let Jerry do it as a straight sci-fi story rather than tieing it into the straight crime series.
It's a Dern LieInteresting premise.
The New Big Hit ComicsAussies In ActionLovely drawing.
Tripalong HoppityFunny, as usual for Emile.
The Death PearlInteresting use of greed.
Milt GreyOkay.
Pilot of DeathOkay.
The Adventures of Jim AtlasThe story is a little off like it's an early attempt at writing. Jim having legs about 2/3s of his body is also a sign of an early art job.
WilberforceOkay.
New Sad SackFunny.
One thing I noticed was how Lt. Pacratt (& some other Lts.) all had fangs. At first I thought he was going for a snakelike look, until I saw his name was Pacratt and realized that they kinda look ratty.