NI and DE question...

[dcent2]

How am I supposed to know the difference of when to use them??

Sonna de ai nante aru no?
is a sentence I have yet to translate because I can't figure out the de.

Back to the original problem though, why would I say, Uchi de hon wo yomu, instead of Uchi ni, and vice versa?

Any tips? Thanks.

[yangmuye]

Sonna de ai nante aru no

deai is one word.

Back to the original problem though, why would I say, Uchi de hon wo yomu, instead of Uchi ni, and vice versa?

Simply because the verb “yomu” doesn't accept “~n”i as a “parameter”.
“ni” has nothing to do with “where the event happened”. (Although it's possible in archaic expressions.)
Its meaning changes depending on the verb.