Are there any recommended books or other sources about research in IT?
For example, I want to do some research on the subject 'Internet of things'. What would be the best way to approach this? What methods should I use?
You do not do research on a topic out of the blue. You must have read enough, understand the basic concepts, the type of problems and the technology, and hopefully be proficient enough to form your own views of how things works, possibly how they should work, how they might be improved or completed. Work can be theoretical (devising new algorithms for faster or more reliable solutions). I may involve developing new concepts, evolving or unifying existing ones, finding new answers to old problems, finding new problems, and hopefully solving them. It may also concern new applications. It may be mostly abstract, or be mostly implementation (if it includes new techniques for achieving results), though it should ideally blend both abstraction and implementation. I probably forget many aspects.
In other words, it is essentially varied and undescribable, depending very much on you own relation with the topic, and the orientation of your necessarily deep knowledge of it.
It may occur that your adviser will serve you a good topic on a plate, with user manual and guidelines to achieve the research and get a PhD. But I would not count on it too much.
So I have 3 advices
And while doing it, always keep an open and critical mind. Question any assertion you find, take notes, make sure you understand what is being said or implied. And do not expect everything to be true. It is not that people cheat (though a few actually do) but we all make mistakes or take unwarranted shortcuts, with the best of intentions.
If you are mature enough to do research in your chosen area, you no longer need to ask your question.
The way I started most of my research was unexpected. I wanted to learn on a topic. I started reading, and after a while thought I would do something differently and started developing my own idea. Sometime I was already very knowledgeable on the topic, but reading critically a paper, I thought that more could be done. New ideas come often from absorbed knowledge. When you have lots of knoledge on a topic, you can also try to unify it, condense it, and it may yield unexpected new results.
Regarding what you should read. I do not know. If you start working on the topic, you will quickly find out from citation and discussions on the Internet. But recall that there are also hidden gems that no one talks about, that may be the key to interesting work. Books are useful to get started on a topic, to get an overview and basic knowledge. But it is not likely that they will be enough to start doing research. For that, you generally need to read research papers, and that may be less easy (people are still struggling with new concepts), but it can be very rewarding.
So you may take any book with some reputation (and possibly pedagogy) to get started on basics. After the first, you should be able to choose the next on your own, in directions you are interested in. But start reading recent research papers as soon as you can, and look at their references. The rest should come on its own.
You can be a great teacher without being a great researcher. The converse is also unfortunately true. But both need to read a lot. Great teachers can write great textbooks.