Yeah, I'm going to second the helmacron thing, and I really dislike 42 not just because of the helmacron.
I was re-reading 42 as research, and not only did the author say ringworm was a parasite (it's not, its a fungus, but then again its narrated by Rachel who thought corn grew on trees in MM2, so I suppose you could argue she's just being misinformed.)
But she wrote Ax's eyes were blue...how did that even get past editing? You'd practically have to not even read the series to know his eyes are green.
I don't know if I can get through the rest of the book, lol.
Edit: book 39, not 31, for buffa-human
The only other book that massively bothered me was 29, the sickness. Medically, there is just too much to even list. I mean, I know not everyone has medical knowledge, but at least do a LITTLE bit of research on surgery procedures if you're going to write about surgery. All I have to say is I'm glad Cassie became a diplomat and not a vet, lol.
And the whole "crisis point" thing made 0 logical sense at all. I mean, I know he's an alien, and you could technically say "well he's an alien," but that only goes so far. At least offer a little explanation instead of just inserting a random "OMG ITS A COUNTDOWN BE SCERRED!" tool. A little bit of research goes a LONG way in writing.
Also, about books like 39 with buffa-human, I really do not understand how creatures are getting morphing ability just by TOUCHING the cube. In all the books prior the morphing ability had to be GIVEN to the recipients by someone who already had it, or knew how to use the cube (Ax and Elfangor.) They had to GIVE it to David, who had been touching the cube probably more than the kids ever did. So how are people like Tom even getting morphing ability? How did the Yeerks get it? (Unless Visser Three got it? Though I was under the impression Tom didn't hand it over, but I could be wrong.)