Featherston is taking part for the third time and librarian Penny Griffin said more than 60 children in the town had taken up the challenge this year, with some already on to their second round of books.
This is the first year Martinborough Library has signed up to the reading challenge.
Janet McAllister, the library's children reading programme co-ordinator, said the challenge would "give the kids that extra little incentive" to pick up a book.
Children who choose to participate can collect from the library a round book review wheel that looks like a pizza with seven slices.
A slice of pizza will be stamped by a librarian after each book is completed by the child.
The child just needs to tell the librarian a little about what the book is about.
When the wheel is full, it can be taken into any Hell Pizza store where the child will receive a '333 Hellthy Pizza'.
Ms McAllister said the children would feel a sense of achievement on redeeming their free pizza, knowing they had worked hard and deserved it.
"And it's something they can keep up at all year."
She said the challenge would run until December and so far 10 children in Martinborough were taking part.
Last year more than 250 schools nationwide signed up to the reading challenge.
