Angelo is one of my favorite quirky characters, and I love him to death for using one of my all-time favorite lines from my all-time favorite movie (Real Genius)! 
 Zach doesn't quite know what to do with himself around Angelo. Walking on eggshells is an understatement, because Angelo has several issues that Zach has to figure out how and when to handle to keep Angelo from bolting, and a few issues of his own. Once Zach figures it out, it's works for them. 
 This story is loosely related to Promises in that Angelo and Zach meet Matt and Jared relatively early on and become good friends with each other. Consider Promises book #1, A to Z book #2, The Letter Z as #3 (sequel to A to Z, where we are introducted to Zach's ex, Jonathan), and Strawberries for Dessert as #4, a story about Jonathan and Cole, Jared's best friend.