Hmmm... that's a difficult question to answer - especially since I don't know how old you are. However, I'll make a few points (in no particular order) that might help with your decision.
- Adolf is definitely not a kid's story. There's a reason for that 13+ rating. It's got some complex themes going on, which younger readers might not fully grasp.
- On the other hand, if your Dad is interested in reading it, he's most likely doing it because he wants to know what you're up to, and what your interests are. It'll be pretty clear pretty quickly that (despite the title) the series far from glorifies Adolf Hitler. It's hardly on the list of skinhead recruitment books.
- While a lot of Tezuka's more mature works have some pretty intense scenes, they're hardly graphic - especially by today's standards. Japanese culture is a little more liberal in regards to depicitions of nudity, but Tezuka is usually careful to convey the power of a scene without going for cheap shock value.
- Tezuka was a humanist. He found value in all life... so two of the biggest themes in Adolf are a) war is terrible and makes good people do terrible things and b) life finds a way.
- The title "Message to Adolf" is playing on the idea that three men with the name Adolf... by chance really, can affect, even indirectly each other. It's a kind of compare and contrast exercise.
- Usually the biggest criticism of Adolf is Tezuka's handling of the Jews. He was trying to make a point, but he just didn't know Jewish culture all that well. So some of the actions have a very "Japanese" mentality to them. Japanese would "right a wrong" in one way...
Jewish people might handle it differently.
- Finally, if you only have one or two volumes, you might want to wait for the upcoming Vertical release to give your dad the whole picture. However, there's some pretty insightful essays written as forewords to each of the old Viz/Cadence books. They might help as well.
I hope that helps. Keep in mind, your Dad probably is just looking out for your best interests, so the best tactic is to be upfront (i.e. no hiding) and discuss any issues in a mature way.