Why you need them
A comic book is a combination of visual art and storytelling; like so, learning how to create a comic book requires for one to study both of the above areas.
The reason I personally prefer reading tutorial books, instead of just watching tutorials online is because the people writing them have worked trough trial and error, and surely studied in one way or another, to provide all of this important information to you. This is even more true for books that are several decades old, when things weren't as easy and quick to be made (or to be learned) as they are today.
People like Andrew Loomis (1982-1959), whose content can only be found in books, are a true goldmine for artists of all levels. Loomis truly gets under the skin of things and thanks to the books he's left behind, he has been a great mentor and influence for countless artists and painters to this day.
Then there are people like Scott McCloud, Michael Mattesi and Joseph Gilland (among many others) who have worked countless hours in the industry of making comics or animation and have also written books to instruct others on how to improve their artistic skills. More specifically, Scott McCloud's "Understanding Comics: The Invisible Art" (published in 1993) and "Making Comics: Storytelling Secrets of Comics, Manga and Graphic Novels" (published in 2006) have completely changed the way I view comics and how I approach the art of making comics myself.
Finally, we have people like Jason Brubaker, who quit his good paying job at Dreamwork Animation in order to pursue the art of making comics... And as a successful indie comic creator, he has written books to help the rest of us who might not be able (or don't want to) join the big companies like Marvel and DC.
How creating your own comic is going to help you
An important note to make here is that you do NOT need to be a master of visual art before you start making your own comic! How many times have we come across badly drawn comics (this goes even more for indie and some Asian ones) but whose story was so compelling that we couldn’t stop reading?
Creating your own comics (and putting them online for people to read) is really going to help you in a variety of ways.
First and foremost, you will get physically better at your craft.
I know it may seem self-explanatory, but many people (me included) tend to believe that the act of reading tutorials or books on anatomy and storytelling and memorizing all that information is automatically making them "level up" when it comes to their skills. That's not actually true. Reading and knowing is not the same as applying and doing things yourself.
Secondly, it will grow your tolerance towards what people have to say (and you will learn to distinguish the actual critiques that will help you advance, from the trolls).
Not all people are out there to get us. I've read many comics with bad drawings but in only one out of the hundred did I see a negative (and downright insulting) comment referring to the creator's artistic skills. In time, you will learn to ignore the trolls and never take their hatred to heart. However if you truly wish to advance, you will also need to be open to people who want to genuinely help you in getting better at what you do. Uploading your comic in comic platforms and sharing it for the world to see, joining groups in various social media and asking for critiques and advice is always the best way to go. In that way, you will also increase your emotional intelligence (in other words, learn to recognize and understand your emotions and the emotions of others, and learn to control your reactions towards certain people and situations) with result making you a better person overall!
Thirdly, it will increase your self-confidence, as well as your persistence and self-discipline.
They say that if you do the hardest thing, first thing in the morning, then the other activities you will have to do for the rest of the day will seem extremely easy, and you will be able to complete them with much more confidence. The same goes for creating your own comic and publishing it online - especially if you are introverted, lack self-confidence or have difficulty trusting in yourself. The human mind truly knows no limits; all you have to do is to just take the first step. As a Chinese proverb says "A journey of a thousand miles begins with a single step."
So, having the self-defeated attitude out of the way, let's get down to business!
For the absolute beginners on human anatomy, I have two books to suggest in this order:
1. Atlas of Human Anatomy [where you learn the skeleton and the bone structure]
2. Figure Drawing: Design and Invention [where you learn figure drawing, as well as the muscles that lie on top of the bone structure]
For an easy and quick access, here are some tag words you can use to find what you're looking for. All images are clickable links to Amazon, where you can buy these books.
The following (and the above) contain affiliate links.