It’s not worth summarizing every book. I took a course at UChicago on how to read a book based on Mortimer Adler’s book of the same name, and the takeaway is that the first reading of a book should be a quick one (table of contents, skimming, dipping into pages). Only after a book is shown to have promise are we then to engage in deep reading which not only involves summarizing but also syntopical reading, which is t…
This may be cultural but I just cannot bring myself write in a book even in pencil. post-its notes for me this is a great idea if I have the discipline
https://siarchives.si.edu/blog/post-it-or-not-post-it
http://libraries.ucsd.edu/preservation/postits.html
It's not clear from these articles how soon damage becomes apparent; I haven't noticed any yet in books which had Post-Its. It may not matter if you don't intend your books to have archival value.
I've tried Book Darts for marking pages, and they can also be used like paper clips to hold notes. I write short notes in pencil, but try to avoid dark leads which make marks hard to erase.