I think this is a very good point!

A lot of the textbooks that I read/refer to are ones that are very relevant to current issues in therapy (before intake appointment, for instance, I was mostly reading books about clinical and diagnostic interviewing techniques, but now have switched more to motivational interviewing, cognitive behavioral therapy, etc.).

In many cases, I don't think I've really been genuinely interested in these topics, but probably more likely a misguided attempt to reduce anticipatory anxiety about therapy in general. In other areas of my life, I follow a similar approach (e.g. if I'm going to get my haircut, then I probably will spend a while reading books geared towards hair stylists beforehand because I feel that the advice/information in there might help me to understand what I need to do to be a "good" customer). In therapy, it is similar (I try very much to be a "good" client -- e.g. not too "difficult", motivated to change, optimistic, etc.).

I also have expectation that therapy should, in theory, be more easily understood than ordinary social interactions. This is highly appealing to me. I think I am pretty sensitive to the knowledge/power imbalances in therapy and sort of believe that I can even the playing field (somewhat, at least) by pretty intensely studying relevant issues in my own time. If therapists are trained to respond in certain ways, then I feel I should be capable of learning why/how they will respond to me, and I can substantially reduce my anxiety about not knowing exactly what to expect.

Unfortunately, I've found that this method has been relatively unsuccessful, so far (most therapists that I've worked with have been at least somewhat unpredictable, despite initial claims of being very highly structured, evidence-based, etc.).