letting books and even projects go
Stoll, The Fruits of Natural Advantage: Making the Industrial Countryside in California
Recommended by L. B-K. who would know!
Iatridis, Teaching Science to Children (2nd ed., 1993)
Has a heavy focus on evaluative criteria and a very lightweight scope and intellectual depth. For example, "evolution" does not appear in the index.
Finishing the Ph.D., there seemed to be a scarcity of topics. Now I'm finding such abundance that I'm actually giving projects away to others. I recently handed off a whole folder of database search printouts to a deserving doctoral student. If I can't do it, then I hope somebody will tackle this project sometime.
I'm on two other tracks right now: children as readers from 1890-1930 and evolution in children's books from the same period.