Frank Brady, James Boswell: The Later Years, 1769-1795
(New York: McGraw-Hill Book Company, 1984), p. 151:
The reader of journals is greedy for the actual: how do other people live, think, and feel? Of all literary forms, the journal comes closest to answering these questions directly: at its best, it realizes dramatically for the reader events and feelings in a way that seems spontaneous and true to immediate experience. Characters shift and shade off into obscurity; events are discontinuous, become prominent and disappear: even the form of the journal is comparable to living, as a day-to-day process whose outcome is unknown.