I receive requests for recommendations in this area fairly often. I don’t feel I am qualified to judge the outputs, but here are three that have come across my path as of late and seem to me very good:
Connor Boyack, illustrated by Elijah Stanfield, The Tuttle Twins and The Road to Surfdom. Recommended ages 5-11.
I.M. Lerner and Catherine L. Osornio, The Secret Under the Staircase, and The Hidden Entrance. Here the age range seems to be higher, maybe 10-12? I feel I could have read them younger than that, however.
Someone should write a bibliographic essay on the books in this category. What else can you recommend?