If I had to give new commies one tip in regards to literature to start with, don't start with the Communist Manifesto. Marx & Engels wrote it for an audience of already committed party members so there are a lot of things they assume of the reader. Also, Capital is a bih to get through, even for the more well read commies. I honestly find that Engels himself is more accessible. Also, Marxists.org is a great site to find free reading materials.
@marxleninmarcy yeah and with centrists or apolitical people I've engaged, I've just tried to talk with them about any misconceptions they may have or talk about how fucked up shit is before going into book recommendations. Haven't had a ton of success totally radicalizing people this way but I've made several people at least more sympathetic to leftists.