I own a lot of programming textbooks. I went through a long phase of buying ones about virtually any technology I was even remotely interested in, therefore I own loads of books about Perl, Ruby, Python, PHP and C, among others. Granted, with many of them I've done little more than flick through them (I find it's hard to get round to learning things like that without some kind of plan, which was what made me eventually start doing a more formal course since it forced a plan on me), but I've seen quite a few.

But of course, not every textbook is equal. Some are great, truly seminal works that are raved about by well-known programmers. Examples include the Camel book (Programming Perl) and K & R (The C Programming Language). Others are rarely mentioned. But what makes a really good textbook? Here I'm going to list some of the attributes that I've found in my favourite and most effective programming texts, and that I think make for a good, effective and informative textbook that makes a good job of getting you up and running programming in a new language:

• Lots of working examples to enter - To learn to program, whether from scratch or in a brand new language, the best advice I've ever heard was that you need to read a lot of code, and write a lot of code. I find that, at least at the start, nothing helps me learn to code in a new language better than lots of examples for me to type in and run, in order to pick up the basic syntax and keywords of the language. After all, that's how many people used to learn BASIC, by typing in listings from magazines, and it's how you learn English as a child - you're exposed to the language, and you copy it, then understanding comes later. One of the best examples of this is C for Dummies, All In One Desktop Reference, by Dan Godkin - it's packed full of loads of great example programs to enter and run that demonstrate the basic concepts well in C.
• Maintains your interest by showing you how to do interesting things - Not many people are interested in learning a new programming language to do something tedious (that said, if someone already has to do something tedious, such as a task at work, teaching them how to write a program to do it for them may well be considerably more interesting for them than doing the task themselves, hence the popularity of scripting languages for automating dull tasks), so a good programming textbook needs to show the learner how to do something interesting. Games are an obvious example, but they can get a bit much - how many different versions of Hangman do people want to create? Simple web apps are also an option with many programming languages. If something needs to be more utilitarian, then if possible it should be genuinely useful for solving a problem (the programmer doesn't necessarily need to have this problem, they just need to see how to create a program to fix it). Frivolous little scripts that do things like recite "99 Bottles of Beer" to demonstrate for loops have their place, but that place is near the start only - by the end a programmer wants to be able to write useful programs.
• Good exercises to stretch the reader - Many textbooks will have additional exercises for the reader at the end of each chapter that allow them to practice their skills and ensure they aren't just copying a listing, but are genuinely capable of writing code from scratch in the language. These are effectively the "homework" assignments, and I've found that these can be far more important at teaching me how to use the language well for actual programming projects than the listings within the book.

These are my thoughts, but I'd be interested to read what other people think about this issue. What's the best programming textbook you've ever used, and why do you like it? What do you think a good programming textbook should have?