"The Art And Skill Of Radio-Telegraphy," by William G. Pierpont, N0HFF, is available as a free download. It is the definitive handbook on learning Continental Morse Code as used in radiotelegraphy. Yes, you missed out on the heyday of The Candler System; what N0HFF is giving away is better.
(Printed, bound copies of the Fourth Edition with a nifty new cover were available at the same site for $11.50 American until they sold them all. Fifth Edition is promised soon).
I recommend this book, which starts out with the profoundly fundamental advice to learn the code by the sound of the letters, not as "dots and dashes," and further to begin picking up word-elements as early as you can. I did neither when I originally learned. Beginning wrong made getting past about ten words per minute a real struggle until I started over, concentrating on code as an aural language, a patterned series of sounds.