Book Meme Deferred

I just realized I had been tagged for a book meme by Daniel and Tonya at Hebrew and Greek Reader. I am supposed to think up the five most enduring or immediately influential books or authors (not necessarily the ones I like the best, but the ones who have shaped my thought through engagement, even through opposition--perhaps often the most important ingredient). I have a few who come to mind immediately, but this is going to be difficult. For a full list or review, I believe I will have to ruminate at least another day or so. If I fail to remember, please, Dan or Tonya, feel free to remind me.