This is an extremely helpful analysis of Evangelicalism that covers almost the entirety of its history. Unlike most scholars Bebbington argues that Evangelicalism had its roots in the Enlightenment and was a product of Enlightenment epistemology, rather than being a reaction to the frigid rationalism of that age. More convincing is his discussion of the role the assurance of one's salvation played in Evangelicalism. Bebbington notes that Puritans throughout the 1600s had had conversion experiences, but that they were highly scrutinized by their coreligionists. The Evangelical breakthrough came when Jonathan Edwards accepted the experiences of those who claimed to be born again as valid in his New England parish. With the conversion of Whitefield and Wesley the assurance of one's salvation came to the forefront of the Evangelical experience. As the movement gained momentum and adapted itself to new exigencies the possibility of conversion was held out to larger and larger audiences and revivalism was born. This was a far cry from the rigid scrutiny Evangelicals' Puritan predecessors would have been subjected to.
In its heyday Evangelicalism would have been considered politically liberal by late 20th century/early 21st century American standards in that it was progressive, fighting for social justice and social transformation as well as emphasizing education and a call to a personal relationship with Christ. Bebbington notes that 19th century Evangelicalism was a "happy religion."
Bebbington focuses on the movement as a whole rather than particular denominations. This is a sound approach, but sometimes one gets the impression that a solitary individual such as Edward Irving becomes representative of Evangelicals as a whole. In reality Irving was something of an enigma in his own time. But overall this is a wonderfully researched work. It might not be indispensable, but it has become something of a standard work on this subject such that many scholars have adopted Bebbington's distinctions in order to describe Evangelicalism: conversionism (the impulse to see oneself and others converted or be "born again"), crucicentrism (a strong emphasis on the atoning work of Christ as sufficient for one's salvation if apprehended through faith), and activism (the zeal to convert others and transform society by reaching out to the poor and the destitute, run orphanages, fight alcoholism amongst the poor, the abolition of slavery, Bible societies, Sunday school for the uneducated children of the slums and factories, child labor laws, evangelism and revivalism).
Overall highly recommended.