Interestingly, the authors deal with this very question to an unusual degree, insisting that English is actually much more rational than many people think.
Always keep in mind that, by way of defending the indefensible, Whole Word, the Education Establishment filled the air with what was basically anti-English propaganda. English is just so crazy, we were told for decades, kids have no choice but to memorize the entire language word by word!!!
I'd say that Russian was about 95% phoenetic, German about 99%, and English about 50%. French is nearly as bad and it's likely that English inherits much of its fubar spelling from French.