La Boheme in Full Score (Dover Music Scores)
This is, unsurprisingly, one of the most-performed operas of all time, for its combination of story elements (boy meets girl, boy gets girl, boy loses girl, girl dies), beautiful melodies, and pure performability. The second act is only 19 minutes long, but it's amazingly complex--check it out in this full orchestral score, a reprint by Dover of an out-of-copyright publication. Bear in mind that there is no English translation, but most recordings will have a copy of the words in English anyway, so they're readily available.