I found a copy of Mr. Hacker lurking in my collection. It's simple text and story serves as great mentor text for young writers. Often children want to write "chapter books" and this is a great text to get into their hands. Katie Wood Ray wisely nudges writers to ask, "What have you read that is like what you're trying to write?"
We used Mr. Hacker as a nudge in our ongoing study of notebook writing... my third graders chose to think about memory writes, quickwrites, word writes, daily pages, and line lifts using this book (after a few weeks of studying each type of notebook entry) as fodder for ideas. They can now use each strategy independently, using text as a launching point for our independent, "ongoing" work as writers. Now, when we're in the midst of a full-fledged study, they have some strategies to use during composing time; to strengthen and hone their skills as writers. Writers who want to have a go as chapter book writers (on their own, not as a class study) could this book's short chapters as a perfect mentor.
After sharing this book, many of my students asked if Cynthia Rylant read this book before she wrote Mr. Putter and Tabby... they surmised that she may have read it for it is, indeed, a cousin text!
Again, the power of searching our libraries for great text!