Rev. W. Awdry wrote 26 books in The Railway Series. He began with The Three Railway Engines in 1945 and ended his authorial run with Tramway Engines, published in 1972.
Awdry retired after the twenty-sixth volume because he was finding it increasingly difficult to develop new stories. The series later resumed when his son, Christopher Awdry, became its author in 1983. Christopher wrote 16 additional books, bringing the numbered series to 42 volumes by 2011.
The number 26 refers specifically to Wilbert Awdry’s main Railway Series books, not every publication connected with the fictional Island of Sodor. Companion works, biographies, Christmas books and other supplementary titles are counted separately. This distinction explains why readers sometimes encounter larger totals when asking how many Railway Series books exist overall.