Some suggestions for more 'out of the way' Mark Twain writings, many irreligious and/or scandalous
Life As I Find It
And this one
The Bible According to Mark Twain
And this one
The Damned Human Race
For an excellent source to great Mark Twain writings that span his entire career, get both volumes of:
Collected Tales, Sketches, Speeches, & Essays
-Zeno