Gender-specific Books?

Husband and I bought a bunch of books for Faris from BookXcess. We struck gold when we found 6 Usborne touchy-feely "That's Not My..." series, all for a very low price.
It came it a set of 3s. One set supposedly for boys and the other, for girls.

Which got me thinking, can books be gender-specific?
One set of the books have pirates and trucks and all things boys.
The other had mermaids and fairies.
I bought them anyways because

1) I thought Faris could really learn from it, despite it being glittery and pink.
2) InsyaAllah we might have a baby girl one day and those books were way to valuable to pass up. We'll save it for her too.

But back to books being gender-specific, do girls only read books on girly stuff and/or about girls and boys for boys?
We live in a world today that is often confusing.
Exhibit A: Man dresses nice, loves to cook; present day conclusion, he's gay. Which may or may not be true.

Are we, as parents, damning our son to this absurd train of thought just because we bought books about mermaids for a boy?

It's mind-boggling.
I grew up reading Oliver Twist and Peter Pan and all other folklores/fables that centered around a male character. Most boys of my generation, like my brother, read of Rapunzel and Goldilocks and even the Sweet Valley series.
Every girl/woman have possibly read the Harry Potter series. And there might be some male closeted-Twilight saga readers.

So why the gender-specific books when knowlegde is universal and objective?
Why label some books "For Girls" or "For Boys"?

It's something to think about.