I once made a deal with a good friend of mine. I read a book of his choosing, and he reads one of mine.
On the bus ride to work every morning and evening I'd be making progress through Clean Code, in the hopes that I would improve my ability to program.
Just because the software works as intended, doesn't mean you've written good code. Is it maintainable? Is it scalable? If another developer were to continue your work, would they be able to understand what you've written?
Robert C. Martin (affectionately referred to by some as Uncle Bob) writes about what he's learned through his long career in software development distilling his experience into practical advice for younger programmers.
The advice in this book has improved my ability to write readable code and even helped me with writing the code that is being used on this very website.