Classicly

'After glancing my eye over the design and order of a new book,' says Gibbon, 'I suspended the perusal till I had finished the task of self-examination, till I had revolved in a solitary walk all that I knew or believed or had thought on the subject of the whole work or of some particular chapter; I was then qualified to discern how much the author added to my original stock; and if I was sometimes satisfied by the agreement, I was sometimes warned by the opposition of our ideas.