The two best textbook providers I've encountered so far: Zybooks and Soomo. At this point, I can't decide which I love more: Zybooks is a phenomenal interactive resource to learn programming; I took an Intro to Java class that used them, and it was a really fun and interesting class, thanks almost 100% to that textbook. It uses frequent practice questions, is super-comprehensible, and has a Programming developing environment built right in; I really can't recommend it enough, and I hope that my future programming classes end up using it. Soomo, on the other hand, makes an incredible Intro to Psychology textbook. It also uses frequent practice questions (which, according to them, has been shown to promote deeper understanding), has an approachable writing style, has a great mobile app with almost all the same capabilities, and the browser site even has a built in text-to-speech reader! Just check out the sort of out-of-the-box questions it asks! They've really made some great advances in teaching methods since I was in school...