[Karellen]

Like most people, I read a book on its own in one form or another, either pbook or ebook.

Recently, since I started cleaning and organising my ebook library, I have been reading two books at the same time. That is the same novel but the pbook and ebook version. I do this to fix errors in the ebook by referring to the pbook.

I had always thought that an Author writes a book, the publisher prints and distributes it, and maybe some regional spelling adjustments were made.

So it came as a complete surprise to me that many of these paired books were different. Reading the pbook and ebook highlighted many, many differences - some were major differences many are minor.

For example as a major difference, I read Arthur C Clarke's Imperial Earth. The ebook version had an extra 6 chapters that were not included in the paperback I own.
A minor difference- I am currently reading The Visitor by Lee Child, and Jack Reacher boards the plane and sits in Business Class (in my pbook) / sits in First Class (in my ebook)

I wouldn't be exaggerating by saying that I have come across easily 100+ of these type of differences over the last year of reading.

So, why does this happen?
Has anybody noticed this also, and what were some of the differences you have come across?