If you've never reached the fifth key in Pac-Man, the conveyor belts in Donkey Kong or the flagship in Gorf, will these paperback guides get you there? Only maybe. For all their detailed advice, these books offer few tips you would not pick up by looking over the shoulders of good players. True, you might decipher the rudiments of unfamiliar games faster by reading about them than by observing them. But good reflexes and fanatical practice are the only things that will keep you from losing your last city in Missile Command or your last humanoid in Defender. The spiral-bound Consumer Guide how-to (Beekman House, $3.98) is visually liveliest, with large color illustrations that are faithful to the look of the machines. The instructions are clear (though only nine games are covered in detail) and there are experts' tips. The 64-page booklet also includes some intriguing marginalia—for instance, the average Pac-Man machine was bringing in $203 a week as of April 1. In Score! (Signet, $2.50), Uston subjects the games to the kind of rigorous analysis to be expected from a Harvard M.B.A. and a blackjack master (he's been banned from some Vegas casinos). He sensibly advises readers to invest a few quarters in learning the games before reading his advanced strategy sections, and his book is the most likely of the lot to succeed at its stated aim. Blanchet and Hirschfeld are young video wizards. Hirschfeld's treatise (Bantam, $2.95), first published last fall and recently updated, covers some games that have faded and lacks sections on new games like Donkey Kong, Tempest and Qix. Blanchet's book (Fireside, $3.95) is current, but skimpy and visually bland. Kubey's effort (Warner, $5.95) is in a class by itself. Though plagued with too-cute prose and a fatal fondness for alliteration, it brims with inside information. Its advice on Tempest, for instance, comes from Dave Theurer, the programmer who led the team that created it. One revelation is that when Atari was developing Missile Command (in which the player defends six cities from attack), the engineers at first styled the cities to resemble a map of the California coastline and named each city accordingly. That much realism video games don't need.