A book isn't something you're supposed to read and finish. It's a set of ideas you develop over multiple reads, if a book isn't worth reading multiple times it's probably not worth reading once.

This is obviously true for non fiction programming books where you can spend years developing a library off of ideas from a single chapter but I was also surprised to learn that it's also true for fiction books. My girlfriend doesn't mind spoilers in novels because she reasons if a book isn't good enough with spoilers it's probably not good enough without the spoilers too.

The goal should be to enjoy reading not read, it's deceptively unproductive to force yourself to finish a book.