C. P. Snow's new novel is one in the series in which Lewis Eliot is both narrator and spectator and this time particularly involved- and it is also one in which Mr. Snow's special talents have their best application. The ""affair"" of the title refers to a small scientific cheat or chicanery (the use and subsequent disappearance of a photograph illustrating a piece of research) and it is the means here of examining many areas of ethical and intellectual consideration as well as personal motivation over and above the morally ambiguous situation which has provoked it. Howard, a younger man, of doubtful character, politics and aptitude, formerly on a research fellowship at a select Cambridge college, had been dismissed- for the use of a photograph which was admittedly a fraud but which he claims to have secured from the notebook of an esteemed, now deceased, professor. While there are those- in the interests of the college- who are reluctant to reopen the case and hold a second hearing, there are others who override the almost autocratic inviolability of the board and Lewis Eliot handles the defense in the proceedings to follow, which involve all kinds of innuendos, speculations, prejudices as well as personal gratifications. It is a scrupulous, equable, stimulating, passionless examination of human conduct- and C.P. Snow's considered almost flat prose is often deceptive so subtle are many of the intentions and revelations which ensue. His audience by now is most secure.