I will be interested to hear Sophia's response, but here is mine. I am an avid follower of this site, totally self-taught with almost 5 years of ever evolving learning and experience. I have several projects "in process" that fall in this category, most are casebound, over or nearly 100 years old. Sophia's hierarchy is what I follow, but to more detail, here's what I've resorted to. I take an inventory of the book, starting at the front cover, working through the "big" things: boards, spine, corners, hinges, endsheets. Then I literally go through one page at a time, and document losses, tears, loose pages, broken threads, etc. I find my first goal is to repair losses and tears, tip in/hinge loose pages, etc. working to have all the pieces for the text block. Once all that is done, if need be the spine then may need attention which can involve scraping/cleaning, PVA and new mull, new spine liner, new endsheets/sewing as needed. So build the text block back and make it as solid as I can. Then I would proceed to address boards/spine/corners and, if necessary, recase. For me, trying to work with the text block in any way without addressing all the miscellaneous "little" things doesn't make sense...just me maybe. Will be interested to see Sophia's response. Good luck.