Learn Vimscript the Hard Way is a book for users of the Vim editor who want to learn how to customize Vim.
It is not a guide to using Vim. Before reading this book you should be comfortable editing text in Vim and know what terms like "buffer", "window" and "insert mode" mean.
The book is divided roughly into three sections:
The first covers basic Vim commands that you can use in your ~/.vimrc file to customize Vim quickly and easily. The second looks more deeply at Vimscript as a programming language, covering things like variables, comparisons, and functions. The third walks through the creation of a sample plugin intended for distribution to other Vim users. The book will always be free to read online right here.
You can buy an ebook (PDF, epub, mobi) version for $8 on Leanpub.
You can buy a paperback copy for $20 on Lulu.
You can buy a hardcover copy for $40 on Lulu.
The book is copyright 2013 by Steve Losh, all rights reserved. You can redistribute it as long as you don't make any changes and don't charge for it.
The source code to the book is available on BitBucket and on GitHub. If you find any mistakes or feel you could improve it feel free to send a pull request, but I'm retaining the copyright on the book, so if you're not comfortable with that I understand.