There are a few volumes that every Catholic should own. These obviously include the Bible, the Catechism, a Catholic Encyclopedia, Augustine's Confessions, and the Catholic Almanac. I'm not sure how often you ought to buy the near year's edition, but if you don't have a recent copy, you should certainly purchase one right away (and early in the liturgical year!)
OSV's Almanac covers an incredible array of information, from a month-by-month review of important events in the previous year, to the liturgical calendar for the current year and a wonderful chart of the "Movable Feasts" on their dates for the next 18 years (anyone familiar with Hemmingway should be amused by the title of this index).
The breadth of topics is impressive - from lists of saints to biographies of current cardinals, the history of the Church (from AD 33 to the present and both internationally and in North America), Catholic demographics of countries throughout the world, Catholics in US government, lists of religious Orders, schools, ecumenical & interfaith issues, etc., etc., etc. Not to mention the (ever-growing) summary of the works of the Holy Father.
Not too shabby!