I am so glad I pre screened this particular book from this series, so I didn't accidentally give it to my kids! Good grief! We have all the other ones, and my kids, 7 and 9 , have read and reread them all, and know so much amazing stuff from them. But this one I can't wholeheartedly recommend.If you've read any of these, you know there is a story telling narrative framework around each topic, like "The planet has been frozen over for generations and now if we just learn enough geology we can save the world" or something similar. This one is "I, Mel, the main character, am so stunningly anxious about my ten question test tomorrow that I am having nightmares in which my fear cripples my ability to save my new friends from evil mad scientist guy" The book literally takes place in her nightmare about the periodic table of elements.In her nightmare, she and her friend, the element Hydrogen, are on a quest to stop the evil mad scientist from destroying the nightmare world, Hydrogen's homeland. Mel is under a lot of pressure from Hydrogen to figure out ways of getting past various element monsters based on their physical properties so they can stop him. The whole effect is to simultaneously teach a lot of good chemistry but also create the impression that 1) it's reasonable to have crippling test anxiety and 2) chemistry is probably a very difficult subject. When she makes any mistakes in her answers in the dream, evil mad scientist calls her a "FOOL!" repeatedly, and Mel calls herself a clown at one point.As you would expect, Mel overcomes her fears in the end, but it's woven through as the main plot point, including on pages 2,3,7,13,14,15,17,33,34,40,42,43,47,48,62,64,79, 81-85, 89, 92, 94-96, and 109. On page 110, Mel turns it around and defeats mad scientist guy....by gaining enough confidence to...give him test anxiety. Then she declares she's learned "not to think of mistakes as the end of the world", and wakes up and makes a perfect score on her test the next day, end of book page 115. So, 28 pages of "fear tests because they could reveal the failure that you are" and 6 pages of "I did a good job studying, so that doesn't apply to me in this case."It's a very damaging message to hand to kids who aren't already suffering from test anxiety. I get that the author was trying to be encouraging to kids who already suffer from this problem. Maybe this would be appropriate for kids in about 8th grade who've figured out for themselves how to manage all the tests they have to wade through, or for a kid who already has test anxiety and needs to hear the "believe in yourself" self-esteem message of our dear old 1980s. However, if you're like me and you've been using this series as an outlet for way younger gifted kids who love learning ... I would skip this one, unfortunately. I was so excited about this one, too, since I'm actually a chemistry teacher myself.