Well, if you're teaching middle or high school you probably have your curriculum/textbook set in stone... But, you can always supplement that! AND YOU SHOULD!
Since I'm talking to math teachers here, I can make a safe guess that you've always liked math and were always pretty good at it. If you were like me (and I know there are some of you out there), you are a former mathphobe. I know what it's like to fear math... especially math textbooks! When typical students opens a standard math text, all they see is a mountain that can't be climbed -- l long paragraphs of 10 point font that they'll never be able to understand, graphs that were clearly done by a computer, x's and numbers flying all over the place... Not even an entire roll of antacids will fix this!
When you are doing something like Survivor Algebra -- where you are asking the kids to read and pre-learn BEFORE you cover the material, a standard text probably isn't going to cut it. Even if you can transcend the hurdle of fear, these books are just not written for the students. They are written for the teachers! We are the ones who make the book selection -- or some committee of teachers above us. If we let the students pick their math books, they'd actually want something they can read and understand -- and not many formal texts would cut the mustard.
If you are teaching Algebra, the solution is free and easy... Warning: Shameless plug coming... Have them use Coolmath Algebra! The online version is free and can be accessed from home. No registration or log-in is required. OR you can get classroom copies! Yep, I've got book versions available now. (It's all VERY exciting!) ;-)
If you are teaching Prealgebra, when you start getting them into the x stuff, you can use Coolmath Algebra... But, before that, I recommend that you try to find some other student-friendly materials to supplement your text. (I haven't written any official "Prealgebra" content yet... But, it's on my long list of things to do. In the mean time, write some stuff yourself! It's a lot of work, but you'll learn a great deal in the process -- and so will your students.
Of course, you'll still want to use your official text for more than just a paper weight... Have them do their pre-learning from Coolmath Algebra, then use your text to assign homework and have them do some text reading during tribe time. If they've already seen the stuff in a friendlier manner, they can LEARN to read their text (in a group setting) after. Teaching them how to read a standard text will really help them out in future courses where they won't have the benefit of more user-friendly materials.
Whatever materials you decide to use, always remember to abide by the copyright rules. Yes, there is what's called "fair use" for the classroom that allows you to use SOME copyrighted materials for a limited amount of time... But, I'm sure you'll be surprised (as I was when I first learned about this) by how tight the fair use rules really are. Read more about copyrights and fair use here - Fair Use. The creators of educational materials greatly appreciate it when teachers are respectful in this area!