Best books on learning Illustrator

The Adobe Help has some good tutorials and sample projects to get you started: https://helpx.adobe.com/illustrator/user-guide.html

You could also opt for one of the many introductory courses on leaning platforms like Skillshare, Udemy, Domestika, CreativeLive and the like …

I really like Classroom In A Book for getting your feet wet (it's basically RTM), then just use Illy as much as possible and soon as you hit a problem search for a youTube video, there's almost always at least one or two for a specific problem, and if you just want to educate yourself in a general way find a youTube user whos' style you like (https://www.youtube.com/@Vektorgarten) and just have fun watching their videos and trying it for yourself. I just watched Monika's mirror Transform one and wonder why the hell I haven't been doing it for years...

Is your question just about books? Or any written instruction? Methods to generally learn Illustrator? Are you into tutorials and step by step instructions or more into a manual?

So you could go for the official documentation. It has documentation approach as well as some written instruction in step by step style as well as videos.

Or the Classroom in a book, which is the official training material used in many places.

You could try the "Vidual Quick Start Illustrator", but it is accompanied by video and probably you will only use the full potential if you actually watch the videos

Then there is the Real World Illustrator, which hasn't been updated in ages, but still is very good foundation with a lot of deep dive techy stuff.

If you want to focus on actually drawing techniques with a lot of reative Input: Vector Basic Training

I would assume you could find demo chapters for almost any book so you can check it out if you find it comprehensible