Hmmm, I dunno if you'd class it as a book or comic series... but I think the very first written literature I read (my dad used it to teach me to read) was The Ancestral Trail.
It's a series about a boy named Richard, pulled from his (our) dimension into a place known only as the Ancestral World to help fight off an The Evil One.
It was actually rather gory and scary for its time and target audience... If you don't believe me, look up the second issue (Tolosh of the Garoon) and remember it's meant to be for little kids and was released in 1993. - http://www.theancestraltrail.com/New%20Pages/Ancestral%20Trail%20Introduction/welcome.php
It's a series about a boy named Richard, pulled from his (our) dimension into a place known only as the Ancestral World to help fight off an The Evil One.
It was actually rather gory and scary for its time and target audience... If you don't believe me, look up the second issue (Tolosh of the Garoon) and remember it's meant to be for little kids and was released in 1993. - http://www.theancestraltrail.com/New%20Pages/Ancestral%20Trail%20Introduction/welcome.php