It's taken us a while to get to chapter books. Neko, as we know, is a bit wiggly, and had a some trouble sitting still through longer stories. Especially when they had few pictures.
When I started thinking about the ones that would be a good fit, I ultimately decided on The Littles. In case you didn't read them as a kid, they are a community of people only six inches tall. They live in the walls of people's houses, but the people don't know they exist. They use what the big people discard to live, and in exchange, they maintain the house—the pipes, the wiring, and all the inner workings. They go on all sorts of adventures, all made even more interesting due to their size.
There are about a dozen Littles book. I remember pouring through them as a kid, always thinking that there might be that slight chance a little family was living in the walls of our house.
Neko has been taken completely by the Littles. We finished the first book, and are anxiously awaiting a delivery from Amazon to bring us the next.