If you're feeling lukewarm about a book, read 50 pages before deciding whether to continue or drop it. Doing this will allow you to try the books you want to read without you feeling obligated to complete them.
Photo by Pedro Ribeiro Simões
Author and librarian Nancy Pearl writes on her blog about her rule:
People frequently ask me how many pages they should give a book before they give up on it. In response to that question, I came up with my "rule of fifty", which is based on the shortness of time and the immensity of the world of books. If you're fifty years of age or younger, give a book fifty pages before you decide to commit to reading it or give it up. If you're over fifty, which is when time gets even shorter, subtract your age from 100 -- the result is the number of pages you should read before making your decision to stay with it or quit.
However, the difference in pages could seem negligible (after three decades, you only get to skip 30 pages!). Instead, just dive in and read the first 50 (or even full hundred) pages of a book. You can clear your backlog by following Pearl's rule, and be doubly effective by making more time for reading.
If you give up on new books too early, you won't reap the benefits of exposing yourself to new ideas and perspectives. On the other hand, life is too short to read bad books, books you don't like, or books that you find repetitive. Don't force yourself to read the whole thing -- if it isn't working for you after 50 pages, finishing it probably won't make it much better.
"Rule of Fifty" [Nancy Pearl's blog]