All fan mail is good, but it's especially delicious when readers admit to a degree of addiction, like these:
“I’ve read it and love it. I couldn’t put it down.” (Katie, age 9)
“Mousenet was a great book! I couldn’t stop reading.” (Sarah, age 10)
“I started to read Mousenet with more of a sense of duty than anything else, but before long I was totally engaged.” Richard (age 72)
Full disclosure: Richard is my brother, which helps explain the sense of duty.