it doesn't have to be your favorite book or anything. It can be any book that you find yourself thinking of with a sense of pride for having read it.
Personally, I am really proud of myself for not DNFing A Little Life and pushing forward. I read a very good chunk of that book with tears running down my face--mind you, I was reading it on my phone during lectures for the entirety of my first semester last year--and I was always on the verge of putting it down just because of the horrible content. Also, it was pretty long; too long, actually. So when I was done, I was simultaneously Heartbroken, broken (just like in general), and relieved. It was truly a feat.
An honorable mention is A Tale of Two Cities by Charles Dickens, because I swear to God I did not understand a single thing about it even 10 chapters in. Charles Dickens is too much.
Les Miserables by Victor Hugo
Tagging onto this comment to ask, is it worth it to read unabridged or will abridged be fine?
If you take out all the irrelevant stuff, Les Miserables is probably only about 300 pages. And I mean genuinely irrelevant. Hugo was mad as a hatter and took off in whatever direction he felt like - long digressions about Waterloo, the Parisian sewer system etc - that really add nothing to the book. They aren't even all that interesting in themselves, as well as having no bearing on the plot, so I think you can read an abridged version and still feel you have read what was important in the novel.
I can’t agree, I think there’s more to Les Mis than just the plot. The digressions were important to the story Hugo wanted to tell and they add a lot of detail and context to the time it’s set in. I don’t think I could read an abridged version and think that I’ve read everything important because it’s part of what’s intrinsic to the book, if not the plot. I feel like you just don’t actually like Les Mis if you’re so dismissive of the digressions, they might not be easy to get through but they’re still a big part of the book.
Of course you're entitled to your opinion but what possible value did that long digression about the Battle of Waterloo have to do with anything? It was pure authorial self-indulgence and added nothing to the story at all. I think he just ran out of ideas and trod water for a while just filling the page until he thought up something else.