TELEVISION SIMPLIFIED, by Milton S. Kiver.
First published in 1946 and revised regularly through the fifties, sixties, & seventies. The earlier editions are black & white only, but are invaluable when restoring a set of that era. Later editions cover solid state & color, so are also essential. I have two: the third edition, published in 1952, and the seventh edition, published in 1973. I refer regularly to both of them.
PRACTICAL TELEVISION SERVICING AND TROUBLE SHOOTING MANUAL, by Coyne Electrical & Radio-Television School, is also excellent. It was first published in 1949, and was regularly updated into the fifties.