I love mushrooms also. Another vegetable I love is green beans. I grow them in my garden every year and I have bags of them in my freezer. I can't imagine not eating them anymore. Green beans, mushrooms and some gomashio over rice, YUM! I'm ready for lunch!
I bet mushrooms and green beans are totally fine :). It's just one book, so Alicia can't possibly tell you every "good" or "bad" food item. One of her main ideas is just to stay away from processed and convenience foods, and also to steer clear of nightshade vegetables. She doesn't mention mushrooms or green beans as nightshades, and I've heard that Shitakes especially are very healthy. The most important thing to remember is to get variety and not be too restrictive :). Trust that your body will know what to do with the whole foods you give it! Telling yourself "I can't eat this...I can't eat that" usually sets you up for a diet that is way too restricted and not as healthy as it could be. If you are worried, I'd research it more and perhaps buy a book on macrobiotics! I love mushrooms and green beans :) mmmm!
Mushrooms are a macrobiotic staple, especially shiitake. I don't know if I could stay vegan--let alone superhero--without them. I have mushrooms several times a week. Green beans aren't common in Japanese/macrobiotic recipes but there's no reason to think they wouldn't be superhero.