Fun with a Pencil by Andrew Loomis. It was written in the 1920's so the language is very dated but the info is still good. It even eases you in to making more realistic figures as well.
Cartoon Animation by Preston Blair. Blair was an animator at Disney back in the early days. It is geared more toward animation but the stuff like cartoon and design elements are still relevant. There are like 50 different versions of this book out there. The older ones have the Disney storyboards and pencil tests, but it has a lot of info that isn't applicable to modern technology. It is still in print.
If you want something more contemporary then there is Brookes Eggleston - Character Design Forge https://www.youtube.com/c/CharacterDesignForge/playlists
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Preston Blair was an animator who made a really good book on animation that helps simplify visualizing things like this. Some videos showing some useful parts:
https://www.youtube.com/watch?v=f6ITCBcWKYA
https://www.angryanimator.com/word/2018/03/20/preston-blair-deciphered/
The book itself: https://www.amazon.com/Cartoon-Animation-Collectors-Preston-Blair/dp/1560100842
Yep! And really anything from Preston Blair. http://www.amazon.com/Cartoon-Animation-Collectors-Series-Preston/dp/1560100842
Also, 'The Illusion of Life' is pretty much gospel for 2d animators.
Honestly, it's not very good. It looks incredibly amateur. I recommend this Preston Blair book, even though it may seem old school and focus on animation:
There's tons of valuable information in that book and if you don't feel like shelling out the money for it, it's easy to find a pdf copy online.