It is hard to know how to pronounce the names when they are read, especially given the different pronunciation of words and letter combinations, which vary by language and dialect.
So, by listening to interviews with Anne and audiobooks, I have collected a few pronunciations to help guide. Note: I don't have any training in language, so I don't know how to create a 'pronunciation key.' I can only put them how they would be sounded out as best by how I can express it.
Mael: Mahl (mawl) or Mail
Marius: Mar-e-us or Mary-us