MIXED MEDIA : * “THE BILLBOARD BOOK OF GOLD AND PLATINUM RECORDS” <i> Billboard Books ($19.95)</i> : Items in this survey of pop-related videos, books and laser discs are rated on a scale of one star (poor) to five (a classic).

Unlike the valuable series of books based on Billboard magazine’s pop charts, this offering is neither fun on a casual, browsing level nor particularly useful as a reference tool. The book lists the records certified as selling gold (500,000 for albums), platinum (1 million) or multiple platinum by the Recording Industry Assn. of America. The problem, for reasons explained in the book, is that hundreds of albums that have sold 500,000 copies or more aren’t included, and only minimum figures are given for countless other best-sellers. So what’s the point?