The cover, created by Jim Hoover. There's a fun detail to find if you zoom in. :-) My old homemade cover and a bunch of other Felix art created by Cy Madrose can be found here. Cy also drew Petula the psychedelic baby hedgehog on the contact page.
Felix is thirteen. When he was three, because of a science experiment gone wrong, he was fused with a fourth-dimensional being named Zyx, who communicates by using Felix's fingers to type. Counting down to a risky procedure to separate them again, Felix blogs about a boy at school he likes, a bully, his mom's annoying boyfriend, the threeness of things, and more, and we meet an Estonian chess grandmaster, Felix's piano genius sister, his gender-switching grandparent, the denizens of the House on Harmony Street, and many other quirky and fascinating folks. Felix Yz was published by Viking Children's, and in audiobook form by Listening Library, in June of 2017. The paperback edition came out June 2018.