John G. Kappas, Ph.D. was the guy who "discovered" variable suggestibility in hypnosis, and this book, Professional Hypnotism Manual: A Practical Approach for Modern Times introduces his modalities of "Physical and Emotional Suggestibility and Sexuality". Prior to Kappas' work, it was generally assumed that as much as 60% of the population "was not hypnotizable", but what he found was that the standard approaches to hypnotism only were targeted to a particular type of suggestibility (the "Physical"), and that with only minor (albeit significant) changes in wording and intonation, everybody could be hypnotized.
It's sort of telling that Dr. Kappas had come to hypnotism from a psychotherapy practice, as there is a lot in these theories which echo Freudian concerns. Kappas defines "Suggestibility" as arising in the child, though interactions with the primary caretaker (usually, the Mother), from birth to around 6. If the Mother presents congruent messages (follows through on punishments/rewards, fulfills promises, etc.), the child will become a Physical Suggestive, and will tend to respond to literal, direct communications ... however, if the Mother presents incongruent messages, the child will become an Emotional Suggestive, and will always be looking for the "hidden meaning" in things, and so will best respond to inferred or indirect communication. From about 6 to 9 the child is in a "socializing" phase where the influence of teachers, classmates, etc. begin to take effect. From ages 9 to 14 the child develops what Kappas calls their "Sexuality" (which, I believe, is an unfortunate choice of words, but is probably due to a Freudian background), which is more about how a person acts or prioritizes than about "sexuality" per se ... this is formed by emulating the secondary caretaker (the Father), with "Physical" resulting in priorities of "relationship/sex - children/family - hobbies - work", and "Emotional" resulting in priorities of "work - hobbies - family - sex". Again, while I think that the underlying dynamics of the Kappasian modalities are valid, I feel they'd be a LOT clearer had he applied different labels to them ... calling the "activity" dynamics "Sexuality" leads to all sorts of misconstrued assumptions about the hypnotherapy (although, to be fair, much of what Kaplan deals with in the "Sexuality" area is "relationship therapy", so there is a basis for this), and repeating the dichotomy of Physical vs. Emotional makes it very easy to create confusion! {n.b.: I found a site that goes into much more of Kappas' theories that I care to here, in case you'd like to check that out!}
Anyway, I had been casting around for an "introduction to hypnosis" book when this free on-line training thing fell into my lap (and, by the way, the offer is still available through the end of August), and certainly found this fascinating. The Professional Hypnotism Manual is no "ooh, wow!" sort of book full of stage tricks or newage "when I was Cleopatra" claptrap, but a serious look at an approach to understanding people (in ways similar to a psychology book), and methods of reaching and helping them. While this is available from both Amazon and their new/used vendors (and, no doubt, from your local major bookstore), you're not getting much of a break from either (it's at full price at Amazon and the cheapest used one is just a few bucks less), so I'd suggest picking it up directly from the HMI bookstore if this sounds like something you'd like to learn!