I had not heard of this series prior to the movie promos. Upon wiki'ing it, it looked like an excellent opportunity for a kid-friendly movie as well as a chance to introduce my son to Greek mythology.
After viewing, I feel the same way. Decent for the adults, with a few innuendos (suitable for teens per the heroes), and very little to scare a 7 y/o who loves Transformers and LotR. He now wants to read the books. I hope they make the others in the series.
Only complaint would be that the...out-world challenges Percy has would be touched on - is it specific to him, or an issue for other demigods as well? Only b/c many children have similar challenges.
I had some idea of the level of violence & sex in the source material; my parents didn't, other than my warning of violence & some T&A. I'm surprised the film got only a R. That said it appears to be a good adaptation of the comic. Costumes, effects & lines were believable. I enjoyed the story, though the setting(1985) & nature of the overall threat were dated, and thus, didn’t have quite the same impact. Nixon's makeup SUCKED - no excuse for it, nor the age-makeup on Silk Spectre I or Comedian. Rec'd only for hard-core comics fans. While I'm glad I saw Dr. M's Mars-fortress in IMAX, I'm sorry I spent the extra $ - not a lot appeared to have benefited from the addl clarity. I didn't need to see repeat shots of Dr M's wang in high-def.