Choose some trivial, popular self-improvement thing you want. Something you wouldn't mind changing about your cognition if it was easy, but wouldn't be heartbroken not to change if it didn't happen. Find some free self-hypnosis audio for it online, and skim a transcript of the script to make sure it's content you're ok with lowering your defenses toward. Then pretend to be the kind of person who just plain thinks it's interesting and worth a try, and listen to it and relax into it.

If you've practiced self-awareness and self-reflection, you will probably have the experience where the parts of your mind you watch yourself with remain normal, while the parts they're watching get lightly hypnotized. If all of you gets hypnotized, that's cool too, you're back to normal at the end of the audio and you might accidentally get a personal change you don't hate.

It's tempting to categorize hypnosis as an intellectual pursuit if you haven't interacted with it much, but it's really got a lot more in common with physical practices than mental ones. As with many physical pursuits, the important bits happen in the parts of human experience that are the hardest to transfer between minds through language, so reading about it will convey much less useful understanding than just giving it a try.

at least, I'm assuming you want to understand it. Some stuff, trying to understand from language is about as effective as trying to "understand" a cuisine by reading a cookbook that calls for a bunch of spices you're unfamiliar with. Skim the cookbook to make sure you're not allergic to any of the known ingredients, maybe, then just go visit the restaurant down the street.

If there's a good book I would be happy to see suggestions, but in my experience I would expect that a book will help you in a similar way to a book on other skills like learning to dance Salsa, do a martial art like Judo, swim or ride a bicycle. 

For hypnosis knowledge to be useful, you need the skill and that requires actual practice and not just intellectual understanding.

That's an interesting idea! I think it's really cool when things come easily, but I know it's not going to generally be the case- I'm probably going to have to put some work in.

My priority is more on the 'high-utility' part than anything. 

Something that seems like it should be easy but is actually difficult for me is executive functioning- getting myself to do things that I don't want to do. But that's more of a personal/mental health thing than anything.