Not, as the title suggests, the actual journal of Hildegard (1098-1179), the best-known female Catholic mystic of the early Middle Ages, but rather a fictional tour-de-force by debut writer Lachman. Hildegard's immense output included books of visions, natural histories, herbal cures, and poetry, as well as innovative chants and mandala-like paintings of cosmic Christian scenes. But she never wrote a journal. Lachman gives us the next best thing--a mocked-up version that captures the flavor of Hildegard and her extraordinary times. The entries cover a bit more than a year, from December 11, 1157, to January 6, 1153; during this 13-month stretch, Hildegard struggles to establish her own monastery, designs a cloister church, weaves a Lenten cloth, mothers a brood of nuns, and heals the sick, all the while performing the many daily offices required of Benedictine nuns through the liturgical year. Subsidiary characters come and go--Volmar, priest and confidant; Rikkarda, a rebellious nun--but the focus is always on Hildegard, above all on her feverish interior life, aflame with visions, premonitions, and symbolic dreams that she attempts to decipher without benefit of Freud. Lest the reader be swamped by 12th-century monastic arcana, Lachman provides a glossary as well as splendidly copious notes (indelicately crammed alongside--not underneath, as is customary--the main text on each page, making the book sometimes hard to read). Trivial as story--nothing much happens, and dramatic tension is nil--but altogether a more accurate portrait of the medieval mind than, say, The Name of the Rose.