First, the reason I think it is not to be considered a "How to Draw Cartoons" book was articulated the best when I asked a 15-year-old boy to browse through the book and share his thoughts with me. He stated that it was a pretty good book, and entertaining with funny commentary throughout, but that the organization of the book wasn't practical because drawings you are asked to recreate begin rather complex, then are simplified to focusing on a single aspect (like facial expression), and then become more complex again. So, if you struggle with doing the beginning of the book, feel free to do it out of order! There were a few places I felt the layout of the book could've been improved. In a section where you given examples of outfits and asked to draw them (or create your own) on a figure, you'll have to flip back and forth between pages to use the pictures as a reference because they aren't on the same spread.
Second, the reason I would not recommend this for younger kids is because the humor, in my opinion, is geared toward teens/adults, referring at points to zombies, keying cars, Gothic lifestyles (somewhat poked fun at in this book), use of the abbreviation "OMG" and another reference of "God help ________ if..." in an effort to be funny. This lack of reverence for the Lord may not be a concern to some, but it is to me, especially coupled with evolutionary ideology in some areas. I allowed my 8 year old son to peruse the book under my supervision and he wasn't interested in reading the words at all, but did draw some cartoons successfully. He didn't appreciate the cave girl cartoon who poses holding a handful of shrunken heads though, and considered that distasteful.
If the questionable content were courteously removed, and the drawing activities rearranged to progress from easiest to hardest to assist beginners, this would've been a 5-star book.
In the interest of full disclosure: I received a copy of this book for free courtesy of Blogging for Books for the purpose of reviewing. I am never required to give a positive review, my opinions are my own!