The first books were written by the Reverend W. Awdry as a way to cheer up his son Christopher, who was ill with measles. The original series had twenty-six books, since expanded to forty-two by Christopher. After a 10 year hiatus, a new book was published in 2007 and again in 2011.
In 2012, the first four books were released in digital format for Apple products in the UK.
Books written by the Reverend W. Awdry
- The Three Railway Engines - Edward, Henry, and Gordon have several adventures.
- Thomas the Tank Engine - A station pilot tries to gain respect.
- James the Red Engine - James gets into trouble and tries to make up for his errors.
- Tank Engine Thomas Again - Life on Thomas' Branch Line is far from dull.
- Troublesome Engines - When the big engines go on strike, Percy is brought in to help.
- Henry the Green Engine - Henry overcomes illness to prove his might.
- Toby the Tram Engine - Toby is saved by the Fat Controller after his tramway closes.
- Gordon the Big Engine - Gordon pulls his act together in time for a royal visit.
- Edward the Blue Engine - Edward is getting old, but proves he has plenty of life in him yet.
- Four Little Engines - The story of the Skarloey Railway engines working together to keep their line running.
- Percy the Small Engine - Percy is fed up of being ordered about and gets a chance to shine when Thomas needs help.
- The Eight Famous Engines - After becoming famous for their adventures the engines take a trip to England, but Thomas almost puts a damper on the trip.
- Duck and the Diesel Engine - A malicious Diesel creates confusion and blames Duck.
- The Little Old Engine - Skarloey returns to find that things have changed on his little railway.
- The Twin Engines - Two well-meaning Scottish goods engines create confusion in the yard.
- Branch Line Engines - Thomas has an accident and a lazy Diesel-railcar named Daisy arrives.
- Gallant Old Engine - The Skarloey Railway engines prepare for Rheneas' return.
- Stepney the "Bluebell" Engine - Stepney of the Bluebell Railway pays a visit to Sodor.
- Mountain Engines - We meet the Culdee Fell Railway engines, and Lord Harry makes up for a silly accident.
- Very Old Engines - Skarloey and Rheneas recall their early days and celebrate their 100th birthday.
- Main Line Engines - Gordon and James get into silly mishaps while Edward surprises everyone.
- Small Railway Engines - Three new engines arrive on Sodor to work a narrow gauge goods line.
- Enterprising Engines - Diesel power may be triumphing on the mainland, but it's quite the contrary on Sodor.
- Oliver the Western Engine - A boisterous Great Western engine gets into trouble.
- Duke the Lost Engine - Peter Sam and Sir Handel recall their old days as a search begins for an old engine.
- Tramway Engines - Percy and Thomas have adventures while Mavis causes trouble.
These volumes were later compiled into Thomas the Tank Engine: The Complete Collection
Books written by Christopher Awdry
- Really Useful Engines - The engines may not have appeared in books for years, but that doesn't mean life on Sodor is dull.
- James and the Diesel Engines - James learns a lesson in acceptance of Diesels.
- Great Little Engines - Sir Handel is not necessarily the life and soul of the Skarloey Railway, as Peter Sam and Duncan prove.
- More About Thomas the Tank Engine - Thomas and Percy fall out after an accident.
- Gordon the High-Speed Engine - Gordon tries to prove he can go fast, and we meet Pip and Emma.
- Toby, Trucks and Trouble - A series of events leave Percy and Toby running the branchline.
- Thomas and the Twins - Thomas meets Bill and Ben on Edward's Branch Line.
- Jock the New Engine - A boastful new engine called Jock starts work on the Arlesdale Railway.
- Thomas and the Great Railway Show - Thomas travels to the mainland for a grand railway exhibition.
- Thomas Comes Home - The tale of Percy, Toby and Daisy's adventures while Thomas is in England.
- Henry and the Express - Henry is ill again and needs repairs.
- Wilbert the Forest Engine - Donald and Douglas desperately need help, but so do the branchline engines. Wilbert is called in.
- Thomas and the Fat Controller's Engines - The engines prepare for the fiftieth anniversary of the Railway Series.
- New Little Engine - A new engine is built for the Skarloey Railway.
- Thomas and Victoria - The Fat Controller renovates an old coach called Victoria for Toby.
- Thomas and his Friends - The Reverend W. Awdry's centenary is celebrated and Pip and Emma become permanent members of the Fat Controller's railway.
All except the last volume were later compiled into Thomas the Tank Engine: The New Collection.
- Barry the Rescue Engine (C. Awdry, cancelled)
- Thomas's Christmas Party (W. Awdry, 1984)
- Thomas and the Missing Christmas Tree (C. Awdry, 1986)
- Thomas and the Evil Diesel (C. Awdry, 1987)
- Thomas and the Hurricane (C. Awdry, 1992)