I've heard so many great things about IFR. Is it necessary for me to read music to understand the concepts in your book? I know my major and minor scales and I'm working on my inversions. Is that enough for me to grasp the material in IFR?
You don't need to read sheet music in order to understand and practice IFR. In fact there isn't a single line of traditional sheet music notation in my entire book. Occasionally I will make reference to the name of a note by saying something like, "This time, let's begin the exercise on the note C#." But even when I do this, it's only because it makes it easier for me to explain the rest of the exercise. But in IFR we learn to create each sound equally in all 12 keys right from the beginning, so we simply don't have any need for sheet music in order to study and create these sounds.
Even your current work with scales and inversions is not required to begin practicing IFR. It's great that you are already exploring that material because everything you study in the world of music gives you a broader perspective on everything else. But there is no "required knowledge" that you need to have before you start with IFR, except for the ability to comfortably play the notes on your instrument.
Improvise for Real is open to everyone, including absolute beginners. There is no sight reading required, and you don't need to know anything at all about music theory to begin. Everything you need is contained in the IFR starter kit below: