When Walter Matthau was approached about cooperating in a book on his life and career he replied: 'I am not yet ready for biographies and such.' "" And Matthau was certainly wise to steer clear of British writer Hunter--who produces a thin, cheesy workup, ""the result of research from Matthau's magazine and newspaper interviews, the comments of his colleagues and viewings of his films."" Matthau's first 35 years or so go by in less than 20 pages here: Lower East Side birth, as Walter Matuschanskayasky of vague immigrant ancestry (Hunter repeats Matthau-interview put-ons with little or no clarification); WW II service; postwar acting studies; modest stage/film employment. In the 1950s he married wife #2 Carol (a first marriage remains in shadow), his stage career progressed (Will Success Spoil Rock Hunter?), while his longtime gambling addiction became ""crippling."" (Whether it was ""a sign of his insecurity, a by-product of his youth or an 'escape valve' from his career worries only he can really say."") And the Sixties brought a heart attack and stardom--from B'way's A Shot in the Dark and The Odd Couple to an Oscar for The Fortune Cookie, with film-by-film rundowns (plot summaries, critical receptions) filling out the rest of this slight volume. Unrevealing on the private life, flatly recycled when it comes to the movies themselves: bland and boring, even for fervent Matthau fans.