i have to say that the josephine mccarthy book 'magical knowledge' is excellent, i really like her style and her information is spot on.
it's direct, honest and straightforward. possibly one of the best books i have read on the subject, although completely different from carrolls, jm takes a mystical approach which seems to embrace my own ethos as well. 
i think in my own evolution, mysticism led me to magick and the two are inextricably linked whereas carrol won't have a bar of mysticism. i do believe in an intelligence within the universe, i don't claim to understand it but i personally feel duty bound to intuit it's will and act as a vessel for it and i think jm comes from the same idea which is why her book resonates with me. 
the magician is pretty much embarking on a process of evolution and communion, he or she is not a god or goddess but an aspect of these intelligences, evoking or invoking. 
carroll adopts a scientific principle to his work, i respect this but sooner or later one has to accept the science can only take us so far, faith is the engine, belief the fuel and if you get this far, the phrase, 'i want to believe' can shift to, 'i believe.'
what you believe is of course subjective and one can argue it is no more truer than anything else anyone believes, in fact magick allows for this possibility, which is why the lone practitioner requires certain parameters to navigate through. these parameters are often found in religion, especially the eastern ones but the western traditions have them behind the dogma encoded in their mystic agendas, gnosticism, kabbala, sufism all have rich frameworks contained within but they are somewhat inaccessible for most but buddhism has a very practical foundation on which to navigate the magickal world. 
the most important is 'no attachments' which can be extended even to the idea of magick, this is a paradox. 
how can one be a magickian and not attached to the idea of magick?
peter carrol spells it out in the idea of 'desire of results.'
this desire is the very thing that makes a practitioner impotent. it's usually the individuals who think they are powerful and dress in the regalia and have the paraphernalia that are the most ineffective. i have always thought the most powerful magick comes from the magickian whom never uses magick. that's the secret of magick, don't use it but understand it is a process that happens and unfolds once a connection is made. 
this is mysticism now i guess but that's just a word and the map is not the territory.
when the magickian uses magick it should be for purposes aligned with the universal will, love, health, protection, life, creativity, these are the natural laws a magickian should aspire to align with.
when one is aligned, these things are beautiful as they are filled with energy that could be collectively termed magick.
i'm impressed with jm's book because she calls a spade a spade, no bullshit, no frills, i may not agree with everything she writes, i've only just started reading it but i respect her immensely for her approach.