I read this in the 1990s while living in Kentucky. Pretty sure it was a library book, although I'm not certain if it was the school or city library. The main character is a young teenage male, in either middle school or high school, Caucasian, living in a small town in the United States. I believe it had pen-and-ink drawings at a few places in the book, and I'm pretty sure it was broken up into chapters. Two things have stuck with me: one is that he is at one point babysitting an infant (maybe his little brother?), and starts reading the dictionary to the child (I remember "pusillanimous" and "susurration" being two of the words, the latter being where he realized that the S words worked best), which calms the child. I think there was a later scene where the child was using a few multiple-syllable words as part of its babble, puzzling its parents.
The other is a running thread in the books where he's doing a science project for a science fair, and his projects keep accidentally breaking things. I believe his overall theme was sources of power over history. I remember one project was a full-sized catapult, complete with a large rock in the holder, which went off when someone (the teacher?) pulled the lever, not realizing it was functional. Another was a steam engine. I think it exploded because he didn't set up the pressure valve correctly. The last had something to do with a fan and a source of smoke, maybe a demonstration of wind power. I remember he initially was going to use a burning rag for the smoke, but found a more elegant solution, I think involving chemicals to generate smoke. At the time of the fair, the teachers were hesitant, knowing what had happened with the other projects, but when he switches it on, the calamity comes when a classmate suddenly leaps back and knocks some things (including a bottle of ink, I think) over. Turns out the classmate had reversed the fan blade, thinking it would cause the smoke to blow back on the protagonist, unaware that a reversed fan blade blows the same direction as before.
I feel like I ought to remember more of the book, but those are the bits that stick out. I remember being particularly impressed with the catapult, and trying the dictionary trick with my little brother (it didn't work as well as in the book, but I learned some new words in the process).
