I most definitely believe that the Overlander series should be as well known and as reknowned as the Hunger Games. These books are suitable for a precocious reader aged 7+ although adults will enjoy them as well.
Gregor is a twelve year old, the man of the house since his father disappeared a few months ago. He stays in their New York flat, looking after his 2 younger sisters Lizzie and Boots (nickname for Margaret...) while their mother tries to earn enough to keep them going.
Then, one boiling hot day, Boots falls through the grate in the laundry room and Gregor follows...
He is transported to a world far beneath New York where they are known as Underlanders, with pale skin and eyes. There he finds cockroaches as tall as him, bats big enough for him to ride on- and rats who think he and Boots are a tasty snack.
He must enlist the help of the Underlanders who believe him to be some kind of hero to escape back to New York safely with his baby sister and find out why his father really vanished.
I loved these books, and sped through them in hours, before rereading them again. It is excellent value for money and you will not be bored any step of the way. They are excellent value as it is only £3.16 per book- far cheaper even than the paperbacks.
I recommend these if you liked any of the following:
Chronicles of Ancient Darkness
but if not, still give them a shot!