Remedial Wizardry is for kids trying to go into their first year of wizardry who are missing some of the common prerequisites about that! It's not incredibly well-written and still assumes the reader is coming in knowing way more than Opalyn actually knows but she may nonetheless want to keep this one.
Item Engineering assumes you already know what a bunch of basic terms and instructions mean--there is nothing about how you could engage in any such act as "impart spin 3/2 to your mana" literally at all--but it is then very meticulous about explaining all of the interactions between all of the kinds of forces that it is telling you to use at all.