Gourse's life of satin-voiced Nat King Cole has plenty of spring and grit, much more so than his Louis's Children: American Jazz Singers (1984). The tragedy of Cole's life (1917-65) lay in his very success as a singer of such lightly mystical pop ballads as ``Nature Boy,'' ``Mona Lisa,'' and even the title ballad here, ``Unforgettable,'' now turning up as a hypnotic come-on for a perfume ad on TV. Before his vocalizing hit big in the mid-40's (today his voice trails behind only Frank Sinatra and Louis Armstrong in airplay), Cole was a pianist vastly respected in the jazz world as the sparkling rhythmic motor of The Nat King Cole Trio. He was always canny about money, and his sudden adulation as the world's top black singer, which made him a millionaire at 30, was too strong to turn down. At his death, from lung cancer, he had 175 unreleased tracks in inventory at Capitol Records, which the company was reluctant to release--because they were too trite. It is still a tragedy that Cole's vocalizing has replaced the 300 or so jazz tracks his trio cut from the late 30's to 1946. Cole was a minister's son, and something spiritual infused his balladry. He was beyond scandal, even when he left his first wife Nadine for the mesmerically influential Maria Ellington (no relation to Duke), although his tax troubles with the IRS tracked some ink. It appears that the IRS- -more interested in Cole having sneaked into a fine house in a fine white neighborhood than in the $150,000 he owed--watched the house rather than attach his royalties from Capitol Records. Cole later had bleeding ulcers from his anxieties. From a rural Alabama childhood to life at the top, with Sinatra as his pallbearer. The early jazz pages are magnetic, and Cole practically sits in the reader's lap throughout. And it's well researched, too.