National Geographic Readers - Caterpillar to Butterfly

Great non-fiction book for my son who craves them. This book is about a second grade reading level- lots of non-standard reading vocab for a beginning reader to know- which can't be helped when you're talking about pupae, chrysalis, and other scientific words! Lots of full color pictures and not a horrible amount of words on each page (don't you just cringe when your kid brings you a National Geographic? "Don't skip, mom!")
I'm trying to get my going-into-second grade son to be interested in reading- and even though he struggles with a lot of the words in this book, the pictures grab his attention and he WANTS to know what it says, so he'll try to read it- if he doesn't know I'm looking..