As part of my great comic book buy from the 70's recently, I picked up a complete run of the Invaders (41 issues).
For those who don't know the Invaders is a comic set in WWII starring Marvel's three greatgolden age heroes: Captain America, the Human Torch (the original android, not the one in the Fantastic Four) and the Sub-Mariner.
Written by Roy Thomas, long-time scribe of the Avengers, X-Men, Conan and Red Sonja, the Invaders is purposely written in a throwback style to Marvel's golden age.
It features appearances by Adolf Hitler. The heroes have sidekicks (Cap has Bucky, Human Torch has Toro) and a lot of the villains are purposely on the cheesy side (Baron Blood, a Nazi vampire being the favorite here).
As the series goes on, new heroes and villains begin to appear and these are by far the highlight of the series. British superheroes Union Jack (best superhero name of all time) and Spitfire, villains Master Man and Baron Blood. It's silver age comics at their best. Light hearted, unafraid to be what they are.
To the best of my knowledge the Invaders have never been collected into a tradeback. You're nosing into a slightly obscure corner of the Marvel Universe here. That said, for those willing to look into back issue collections online, it's not that expensive either.
I picked up low quality copies that averaged about a dollar an issue (or about a third of the cover price of a brand new comic). If you want high quality copies of course it'll cost more, but I went with Good quality comics that I wouldn't feel bad about packing around with me and actually reading.
There's more old school reviews on the way, with the rest of my big-ass comics buy to look at. I also got an awesome new Marvel Masterworks that I will be reviewing in the coming days, so stay tuned.