If you haven’t figured out the core argument you want to make with your book, or what its most significant contribution is, DON’T FEEL BAD. This is the thing almost everyone struggles w/ & it’s literally just a part of the process of writing a bk. You won’t be at 100 right away.
If you’ve been sitting with your manuscript awhile (like years) and still aren’t sure what the central point is or should be, try my method for clarifying argument here: https://link.medium.com/2OlrIkiAfdb
If you want to go deeper than that, look at Chapter 3 of Scott Norton’s DEVELOPMENTAL EDITING ( @UChicagoPress) https://press.uchicago.edu/ucp/books/book/chicago/D/bo5604692.html
And as @ginasue pointed out (and I note here https://www.insidehighered.com/advice/2019/08/06/why-you-shouldnt-immediately-try-convert-your-dissertation-book-opinion) talking to other ppl abt yr project and finding out what they think the major takeaway is can be extraordinarily helpful
“Talking to ppl abt yr project” can take many forms: writing groups with friends/colleagues, putting pieces of the project thru peer review (e.g. journal articles), talks and conference presentations, teaching the material with students, tweeting, blogging, etc
You’re not a lesser scholar if you don’t have it all figured out from day 1. Nor for depending on feedback from others. That’s what scholarly community is FOR
Why am I tweeting this thread in the middle of the night? Blame the same person who prompted this one https://twitter.com/lportwoodstacer/status/1098133435179245568