Great questions, thanks!! I love ee cummings' poetry and did my first published article on his "what if a much of a which of a wind" in the Explicator, a journal for the explication or interpretation of poetry. I had also done a college presentation on that poem and "if everything happens that can't be done" and my professor worked with me on writing it up for the journal. I learned more about the incredible depth of cummings' poetry, and about writing in general, in the next weeks of rewriting and rewriting for Jeanne Nichols than I had throughout school until that point. It takes time to fully see what cummings is doing in the sections of his poems; setting off sections in parentheses from those outside the parentheses is something he loves to do. So, returning to these poems is a complete joy for me, especially since I had not done even my bachelor's in Theology, much less my graduate work (Systematic Theology) when I wrote that first article!! To return to him now, after 42 years as a hermit reflecting on God and the nature of eremitical solitude is to realize even more clearly how profound cummings' theology was right from the get-go all those years ago.
So, regarding your questions, if you read the whole poem again and then focus on the parenthetical section dealing with books in each stanza, what you will see is that cummings is setting "book learning" off against an almost ineffable experience of two people profoundly in love with one another. What he tells us is that book learning couldn't have planned this or instructed one in "how to" here. A loving relationship is a living, growing thing, and even the smallest bud falls outside the scope of book learning; books, after all, "don't grow". They are not alive. But relationships and those that enter into them are living things, as is love; these grow, falter, wither, die, and sometimes blossom in fullness. One cannot capture or come to know love in or through a book, not love's wisdom, beauty, challenge, joy, or its meaning. Books are meaningful, yes. Cummings affirms this, but at the same time, the "we" he is celebrating is far more full of meaning and life than any book could ever be. One learns to love only by loving, and when two people come together in this way, it is meaningful and joyous beyond imagining or telling.I don't think e e cummings is anti-intellectual; at the same time, he understands the place of the intellect and the ways life and love surpass it. He writes consistently in many of his poems about the ineffable nature of the person who is truly alive. Being truly alive, and so, an individual, conflicts with those who are merely "everyones" or "anyones". Similarly, I don't think cummings was describing a strictly mystical experience of union with God, though I have to say that his sense of what happens when two persons come together physically as well as psychologically and spiritually in love is very consistent with what happens when a person experiences union with God. Cummings's work is about love and coming to fullness through love. While that is true of human relationships, it is even more true of the Divine/human relationship. Thus, even if cummings was "merely" writing of human love, his poetry can also be used to reveal the telos or goal of Divine/human love.
What it means to be a "we" is that to be a complete human being, a human person who is known by and knows God, implies being united with God. On some very foundational level, God and the human person are indivisible. Being one and being a we coincide. When I write about the silence of solitude as goal, this is what I am talking about --- a human person coming to fullness of being and meaning, who is therefore living out the joy of a loving union with God. Solitude here involves oneness of being, meaning one is whole, complete, and holy because one lives in union with God. The potential for this is always present within us, just as God is always present within us. We can learn and choose to be those "going it alone" or standing without God, or those who are truly dependent upon God. The paradox is that true individuality means existing in, from, and for God and those God loves, while standing without God has to do with being individualistic, egoistic, and isolated or even alienated from our deepest self and others, including God.For the hermit, then, there is a vast difference between individualism, egoism, isolation, and individual wholeness or holiness, theonomy, and solitude. I think cummings captures these two with his contrast between an I that stands yearning and apart from others, and a "we", where we become fully ourselves only in a relationship constituted by love. The height of this latter state is found in the "we" of union with God. I suppose that my own experience could be called mystical, yes, since it is the fruit of an experience of the profound Mystery that lives at the core of my being and created the universe. In this coming to be our truest selves, there is certainly a union involved ("we're wonderful one times one"). At the same time, I know from past prayer experiences that there is a good deal more in front of me. This recent experience is full of peace, hope, and promise ("there's somebody calling who's we") -- though I cannot begin to imagine it, of course.