Arnold's Valentine is one of Hey Arnold! chapter books based on the episode "Arnold's Valentine". It was written by Craig Bartlett and Maggie Groening, based on a screenplay by Steve Viksten and Rachel Lipman, illustrated by Tim Parsons, with cover by Tuck Tucker, and Teale Wang.
The novelization of the episode. They left out the puking and the subsequent prettification of Helga, but they put in more about Arnold flat-out saying that he likes Helga-Cecile and has a really good time with her. Helga also has pink hair when she is Cecile. This could possibly be because Arnold could've easily been able to tell it's Helga in the episode.