I do not recommend Carlos Eire's The Life of St. Teresa: A Biography.
It does the same cute trick in the title that Arriving at Amen does. Where Arriving leads you to expect some story and argument about how the author became Catholic, given the title, the author instead regales you with techniques for increasing your holiness apart from the actual process, you know, whereby the author arrived at amen.
Similarly, you'd expect a book titled The Life of St. Teresa: A Biography to be about the life of St. Teresa -- indeed, a biography. But it is instead about the "The Life" of St. Teresa, i.e., about St. Teresa's autobiography. It spends time on how St. Teresa's vida was written, is organized, was revised, was received, has been handed down over time, has inspired movements, has been interpreted in art, and so on. But if you already knew a fair amount about St. Teresa's life, this is not going to contain many revelations. I learned new things, but overall the process felt very lightweight.
Similarity between Teresa and 'heretics': " It was the similarity between her method of prayer and that of the Alumbrados—a homegrown Spanish heresy—that led the Inquisition to investigate her and to demand that she explain herself clearly in the autobiographical text that came to be known as the Vida. The Spanish term alumbrado means “illumined” or “enlightened.” The Alumbrados were men and women who were hunted down by the Inquisition in the sixteenth century, ostensibly for observing certain methods of prayer and claiming to be illumined by the Holy Spirit or to be actually deified through their union with God.... The identity of the Alumbrados is a controversial issue. Although there were various individuals who did indeed share common approaches to prayer and certain claims about their closeness to the divine, it seems clear to many scholars that the Alumbrado heresy was not as unified or organized as the Inquisition assumed. Consequently, experts still disagree on how to interpret the records kept by the Inquisition in its pursuit of the Alumbrados. Disagreement is strongest when it comes to the question of whether or not they all shared the characteristics and beliefs that the Inquisition ascribed to them. Were there really Alumbrados who believed that they could reach union with God and that this union divinized them and made them incapable of sinning? Were there Alumbrados who engaged in immoral behavior because of this antinomian belief? Did they all deny the existence of hell? Regardless of how these questions are answered, no one can deny the fact that hundreds of individuals were pursued by the Inquisition and convicted of alumbradismo during Teresa’s lifetime, and that many of those punished by the Inquisition had read some of the same devotional texts as Teresa and observed approaches to prayer very similar to hers. Moreover, not everyone suspected of alumbradismo was found guilty, and some of the individuals caught in the Inquisition’s dragnet—such as Ignatius Loyola, founder of the Jesuit order—later proved themselves to be leading figures of the Catholic Reformation. Distancing herself from these apparent connections was essential for Teresa, and this gave shape to the Vida. The key parallels with the Alumbrado heresy involved approaches to prayer and the outcome of those approaches. As the Inquisition saw it, the Alumbrados were far too keen on the methods recommended by Francisco de Osuna in his Third Spiritual Alphabet."
Teresa and the Third Spiritual Alphabet: "Much of the terminology employed by Teresa can be traced to her beloved books. One in particular, Osuna’s Third Spiritual Alphabet, had provided her not just with terms but with approaches to prayer. Her use of terms such as “mental prayer,” “meditation,” “recollection,” “prayer of quiet,” and “prayer of union”—which can be found in Osuna’s text—is much more than mere categorization. The terms, the methods and states they attempt to describe, and the experiences claimed by Teresa are all one and the same, indistinguishable from one another."
Conversation with God?: "This text was intended as a manual for Teresa’s nuns: it was a how-to book, much more focused on outlining the various steps to be taken in mental prayer. In this text, she emphasizes the ineffability of this approach to God. Somehow, “without the noise of words,” she says, the human faculties are suspended in mental prayer and “they bask in joy without understanding how they do so; the soul is set ablaze with love, and doesn’t understand how it loves; it knows it enjoys what it loves, and doesn’t know how it enjoys it.”
Not giving a shit about miracles: "Whether or not Teresa defied the law of gravity is immaterial."