Mulling over possible approaches to the life of Thackeray, the novelist Margaret Forster (Georgy Girl, Fenella Phizackerley) eventually ""realised I had no desire whatsoever to know how far Thackeray was telling the truth about himself,"" and decided to ""read no more of 'the other side.' "" Instead, she embarked on what may best be called a first-person biographical pastiche, based chiefly on Thackeray's letters and the reminiscences of his daughter, Lady Ritchie. Forster's assumption that impartial consideration of various sources would have been intrinsically duller than running away with the subject's own prejudices is both odd and disturbing. But her attempt is not without its attractions. For one thing, her imitation of Thackeray's stylistic mannerisms is generally convincing despite occasional anachronisms. There is something remarkably right about the rhythm of narrative and digression, and the favorite Thackeray gimmicks--the fictitious ""Michael Angelo Titmarsh,"" the conversational interjections and elbow-jogging rhetorical questions--seem to appear of their own volition. Nor is the supposed self-portrait without warts: Thackeray's attitude toward the American slave question (""Blacky being my man and brother and so forth"") is confronted head-on, and the uninspired industry of books like The Newcomes and The Virginians is if anything overemphasized. Forster's accounts of Isabella Thackeray's mental collapse and the protracted quarrel with Dickens over the Yates affair are fair-minded and affecting. On the other hand, she tones down the religious severity of Thackeray's mother and occasionally tries to second-guess posterity on such issues as the subjection of women. There are also some lapses of grammar which--despite Forster's sanguine disclaimer that she was following the ""relaxed and often racy"" language of the correspondence--are nothing but an annoyance. The illustrations are Thackeray's own, and generally appear just as arch and patronizing as they did in their original contexts. This is a literary curiosity of real if erratic charm. But not, one hopes, a harbinger of other books of the kind.