The political pressure on Christians is increasing worldwide every day. As long as you can still buy Christian books freely,you should use this. The freedom of buying books can very quickly be over, as history has shown often enough. So do not wait to long!
Catholic english speaking Christians should at least have the following books:
Baltimore Catechism No. 3
Blessed Be God (Missale/Prayer Book)
WARTIME PRAYER BOOK Fulton Sheen