There are quite a few individual people & yoga schools that get hold of, sell, & promote books with advanced spiritual practices, from other sources.
I once had a big 'animated talk' (!) with someone who was doing just that: using someone else's books in their teacher training course, with no understanding of how to actually use them. Plus, handing out other intellectual knowledge of chakras & such, that were, well, laughable.
The problem with freely including, & nilly-willy practicing, the techniques in these books, is that, unless you have actually been trained how to use & apply these techniques by practicing them in a structured & methodical manner...you, or the teacher, don't really know what they're doing. These techniques are usually practiced in a safe environment, like a proper ashram that has the authority to do so. Or with a highly trained & knowledgeable teacher who has a strong sense of what to teach a person, & when.
And this is the important part:......the teacher knows what to teach, how to teach, what to have the student do, to get to the stage of the beginning advanced practices. A volatile person, for example, is definitely not going to suit techniques that stir up the internal energy to a point whereby that person is not able to handle their temper. And, someone who has not practiced meditation, simple mantra, & has not started the gentle release of the immense number of thoughts that everyone has inside them, can become a bit unstable emotionally with the very advanced techniques.
The most advanced techniques are working on the very deep contents of mind....not just those superficial layers, and, those superficial layers need some release before the advanced yoga is taught. This is generally not understood, but is a most important point. Start at the beginning. Become conscious first, tidy up your body, & emotions, work on the subconscious via meditation....then when the time is right, find an experienced teacher for working on the unconscious realms, for the advanced spiritual yoga practices are working on the unconscious mind. This part of the mind is beyond intellectual or emotional analysis, & a process is used to access & traverse it....and, guess what?? ....that knowledge is not in books.
Do not neglect a small daily practice (sadhana) for it will strengthen your body systems, and, there is a correlation between body & mind. For example, the chakras have a relationship with the endocrine system, the spiritual energy channels (nadis) have a relationship with the nervous system. Build up & harmonise these before attempting the glamorous advanced yoga. That's what the physical aspects, the postures (asanas) & shat karmas (body cleansing practices) are really for. And, the correct pranayama will build up & harmonise a part of the nervous system: this in turn will bring in the spiritual energy, via another part of the nervous system.