Yeah, I'm one of the few people in the world who totally agrees with you on this.

Although the boy protagonist is 11 to 12 years old and has almost no friends or social life outside his family, and the Underland, so teenage girls (think they) can't relate to him.

And the first book has an excuse plot where the kid just suddenly fals down a whole in his apartment laundry room for no reason other than "it was destiny" and discover the Underland.

And his toddler sister, nicknamed Boots, is also with him. So that makes it seem kiddish.

The whole series in general is like war trauma, but for children!

I have been a massive fan of the seres since 2003, when I was twelve, so by the time the last book came out, I was sixteen, but didn't consider myself "too old" for it.

And I've been a part of the fadom ever since. I've uploaded and deleted (when I realized they were crap/I got more experienced) dozens of fanarts on deviantART since 2006.

Also. The font on those covers suck, and cement the series image as a kiddish talking animal series. The intial printings had the metallic ones with the flat-top font. Or at least the compromised smaller all-gold font with Times-New Roman type font, from the most recent printings, are better.