I'll be honest- If it isn't a topic that interests me, I won't do a book for a single topic. I will do podcasts though! Some of my favorites for historical topics are Throughline and Stuff You Missed in History Class.
Recently I have found myself reading books for single lessons or units. But- to Katie’s point, I have to be interested. I do also recommend Stuff You Missed in History Class- awesome podcast and always learning something new from it!
So, I tend to read more over the summer in preparation for the school year. It is awesome that you have time to read in preparation for a lesson or unit. One of the books that I read over the summer that encouraged changes in lesson planning was Cuba: An American History by Ada Ferrer. I just learned so much...
I find myself in this boat. Looking at Christopher Clark's Revolutionary Spring about 1848 revolutions. I'm trying to think of it as a long-term investment. I don't feel like I really understand a topic unless I've spent book-length time in it. So, if I plan to teach for another 20 years (heaven help me), and I read 3 history books a year, it'll pay off in later years. Plus, it's interesting. But I do feel your pain of drinking from a fire hose. It's an impossible task.