Breakdown of Warum seid ihr von dem Buch so enttäuscht?
sein
to be
das Buch
the book
ihr
you (informal plural)
von
from, of / by (agent in passive clauses)
Questions & Answers about Warum seid ihr von dem Buch so enttäuscht?
Why do we use von with enttäuscht? Could I use durch since it translates to 'by'?
In German, the adjective enttäuscht (disappointed) takes the fixed preposition von to indicate what is causing the disappointment. Even though English speakers might intuitively reach for durch (through/by) or in (disappointed in), you must memorize the specific pairing: enttäuscht von.
Why is the noun phrase dem Buch in the dative case here?
The preposition von is a strict dative preposition. Whenever you use the combination enttäuscht von, whatever follows must take the dative case. Since Buch is neuter (das Buch), the article changes to dem.
Could I shorten von dem to vom in this sentence?
Yes, absolutely! Saying Warum seid ihr vom Buch so enttäuscht? is very natural and common in everyday German. You can almost always contract von dem into vom unless you are strongly emphasizing the specific word dem (like saying 'from that book').
Why does so enttäuscht go at the very end of the sentence?