To start at the beginning, there are three works CONCEIVED AS WRITTEN WORKS that are nearly universally placed in the Western Canon. I use the conceived as written works to distinguish them from other works which, though considered in the canon, are in the end written versions of oral stories and traditions. So we're setting aside your Homeric epics, your Beowulfs, your Platos. These are all fantastic works, but they are not works native to the page.

You can base much of Western Literature around three formative works: Don Quixote, The Canterbury Tales, and The Divine Comedy.

Each of these works established forms and archetypes that have persisted throughout the centuries and other authors have, consciously or not, emulated to this day. These three works are rather important in properly understanding and digesting nearly everything that comes after them. In other words, they form an important context and reference point.

After those three, you can really select at your leisure. Many historians and academics have compiled helpful lists to get you through it all. Harvard's five-foot shelf is a fantastic starting point, based on the idea that a thorough and well-rounded classical literary education can be had in one's lifetime by reading 15 minutes a day from a selection of works that will fill one five foot wide bookshelf. These books are all in the public domain, and are freely available. I quite like the 7 inch android tablets as perfect for reading on, a Google Nexus 7 is the size of an average sized book, though much thinner, and at a better then 1080P screen resolution has crisp, clear text and costs less then 200 dollars. You can load up every book on the five foot shelf list and leave it by your couch or your bed, and read a bit every time you feel like it, a very worthwhile pursuit.