Paul Haffner has put together a great book called the Mystery of Mary. It is over 250 pages and covers topics of Marion theology such as her perpetual virginity, the Immaculate conception, among others, and how they fit into the Catholic faith and revolve around Jesus Christ. The author Haffner is well educated, and has degrees from Oxford as well as the Gregorian University. It is well written and well documented with sources. Get a copy while you can.