For 〜ものだ, it is used when the thing is of common sense, and usually is used to advice or remind people of morality,principle of life,etc. 〜ものだ： 〜が一般的な常識だ （人に対して注意する時によく使われる）
It is not necessarily a stern usage(e.g.scolding), it can be an advice or recommendation with the meaning "should". 〜ことだ ： 〜ことを勧める 、〜ことが必要だ
べき seemingly implies somewhat more of 'should'ness, while 〜ことだ is literally like 'this is about 〜(gerund)', and really is the emphasis on something being required. In a way, ことだ is even more imperative.
#5489 when you are scolded, you might be told in this way. あなたはこれをよむことだ。（そうすれば全てがわかる。。とかかんとか）Don't you think so?
#5489 is weird. No one would say that. あなたはこれを読むべきだ would be okay,
thanks for the correction miki. changed.
is #5489 correct? xephyer, did you make up the japanese example?
often used to emphasize some important thing
seems pretty identical to 〜べき 読むべき = 読むことだ = you should read
I think my translation is a little rough here ^^; Incidently this is much the same as "An it harm none, do as ye will shalt be the whole of the law."
Formed from verb + koto Negative sense etc possible. V = verb.