One Fish Two Fish Red Fish Blue Fish by Dr. Seuss (1960 edition)

Most of Dr. Seuss’s books had only his hand lettering on the cover, but this title uses a font. The letters appear to match Cambra on page 18 of the “Alphabet Thesaurus, Vol. 2” published by Photo-Lettering, Inc. New Century Schoolbook was used for the interior of this and many of the other first edition Dr. Seuss books.

As of 2001, over six million copies of One Fish, Two Fish, Red Fish, Blue Fish had been sold, according to Wikipedia.

Update: Stuart Sandler informs me that this is actually Filmotype Major, released as a photocompositor font in 1951. It was recently revived by Rian Hughes and released under the new digital incarnation of the Filmotype foundry owned by Sandler.

Update Jan 19, 2016: Steve Jackaman of International TypeFounders adds

We produced several new Dr. Seuss fonts in digital form about 20 years ago, based on just a few glyphs from their multiple logo styles and early examples.

Dr. Seuss editions after 1995 may use these ITF fonts.