Jeffrey Ostrowski is a real-world parish musician who has seen a need for a super entry-level book of sung propers. He has produced this with Lalemant Propers, explained in more detail below and offered for sale and free download here. Essentially, this book picks mode II and sets the entire liturgical year to it. This is excellent practice for chanting and singing. I can easily imagine that there are certain parish contexts in which this would be valuable. Even if you are doing more complex versions, sometimes you just need to sing the offertory in the simplest way possible.
Nathan Knutson, cathedral and diocesan director of sacred music, performing artist, father, lecturer on sacred music