Comic book letterer and historian Todd Klein has released what he calls an "online book" on his blog: The Art and History of Lettering Comics.
Neil Gaiman, who employed the lettering services of Klein on his legendary Sandman run, among other projects, writes in the introduction:
If you have even a passing interest in lettering, Todd Klein's writing on the subject and the people who he knew and the people he only knew through their work is gripping. If you want to letter, if you make comics, this is a masterclass in what comics lettering is and can be.
I would add that even if you don't think you have a passing interest in lettering, if you do have a passing interest in comics, this thorough look into the art of lettering will inform that interest far more than you'd suspect.
I especially like Klein's history and analysis of letterers' work on comics' logos. Particularly Otto Pirkola, for Harvey Comics, Ira Schnapp, for DC Comics, and Artie Simek, for Marvel Comics, working with Sol Brodsky.
Comic book writer and historian Mark Evanier, in writing about Klein's book, wrote:
Jack Kirby once said of longtime Marvel letterer Artie Simek, "Often, the best art on a page of comics is what Artie put there."