Karl Seguin has released the official, and completely free, Foundations of Programming eBook.
Although simplistic, every programming decision I make is largely based on maintainability. Maintainability is the cornerstone of enterprise development. Frequent readers are likely sick of hearing about it, but there’s a good reason we talk about maintainability so often – it’s the key to being a great software developer. I can think of a couple reasons why it’s such an important design factor. First, both studies and first hand experience tell us that systems spend a considerable amount of time (over 50%) in a maintenance state – be it changes, bug fixes or support. Second, the growing adoption of iterative development means that changes and features are continuously made to existing code (and even if you haven’t adopted iterative development such as Agile, your clients are likely still asking you to make all types of changes.) In short, a maintainable solution not only reduces your cost, but also increases the number and quality of features you’ll be able to deliver.