Mr. Springer, a dour consumer watchdog type who is solidly factual rather than innovational (last time around we called him commonsensical), now turns his cautionary pen on the mutual boom, those attractive and sometimes confounding funds which have gone so far so fast. Springer flatly states that their rapid growth is the ""most amazing investment accomplishment"" of this century and even skeptical holdouts like Merrill Lynch have jumped on the bandwagon in recent years. Or is it a bullwagon? As the title indicates, Springer believes that mutual funds have been oversold and overstuffed by market propagandists; that they are not always the ideal portfolio item for individual investors; and that there is considerable under-the-counter chicanery involved in the industry. Springer, who cites various studies (a Fundscope magazine survey, a Wharton School performance analysis, an SEC report) supporting his view, is always reasonable, ever admonitory, never vociferous -- very much like his last several books which include If They're So Smart, How Come Your're Not Rich? and Consumer Swindlers. . . and How to Avoid Them.