Another such case is Hugh Lofting, who wrote a Dr. Doolittle book a year from 1922 to 1928, when he sent Dr. Doolittle off to the moon and had Thomas Stubbins come back to Earth without him. After that there was a five-year gap before he wrote Dr. Doolittle's Return. Apparently Lofting had intended Dr. Doolittle in the Moon to bring the series to an end . . . but he didn't succeed.
Another such case is Hugh Lofting, who wrote a Dr. Doolittle book a year from 1922 to 1928, when he sent Dr. Doolittle off to the moon and had Thomas Stubbins come back to Earth without him. After that there was a five-year gap before he wrote Dr. Doolittle's Return. Apparently Lofting had intended Dr. Doolittle in the Moon to bring the series to an end . . . but he didn't succeed.
I didn't realize there was such a long Dr. Doolittle series! I read a few of the books as a kid, and liked them, but I never thought to look for more.
(Sorry for the delay responding; your comment slipped through the metaphorical cracks!)